The plan of salvation through the line of Abraham was revealed in the Abrahamic covenant. And the covenant is Unconditional.

Let's fast forward to the 40 years in desert, where we have Moses preparing the Israelites to go into the promised land. It is said that 70% of the bible is the story of Israel. Maybe theres something in the story of Israel God wants to show us.
Here we have God telling Moses to record a song and teach it the generations of Israelites so the song will be a witness to God of the idolatry and wickness of the fathers to the future Israelites, all before they even apostatised.

God knew they were going to apostatised even before they have done it, so why did God chose the Israelites for this plan of salvation? Did God think that they will perform better than the gentiles?

Of course not. He chose them because He has predetermined to set His love on them, no other reasons. This is Sovereign Election again.

Sure enough, Israel subsequently apostasised for hundreds of years. Then we have God giving indictment after indictment in the books of the prophets.

We cant go through all of them, but I just want to point out a few verses to show the plan of the new covenant.
Can you count the number of "I will"s in all those prophecies regarding the new saving covenants? God will cause future Israel to repent, when He sends His Spirit to regenerate them.
This is an expansion of the Abrahamic covenant and the basis of the new saving covenant even to the gentiles.

The doctrine of election throughout the bible is deafening! Calvin couldnt have invented that even if he wanted to.

The bible is so clear when we understand the covenants. I hope you have been blessed by this.

The LORD did not set His affection on you and choose you because you were more numerous than other peoples, for you were the fewest of all peoples. But it was because the LORD loved you and kept the oath He swore to your forefathers that He brought you out with a mighty hand and redeemed you from the land of slavery, from the power of Pharaoh king of Egypt. Know therefore that the LORD your God is God; He is the faithful God, keeping His covenant of love to a thousand generations of those who love Him and keep His commands.- Deut 7:7-9

the Church can never replace Israel....I thought the in-grafted branch scripture is quite clear on that....

Well God started off in Romans 11 with the context of "by no means!"

Romans 11:1-2
1 I ask then: Did God reject his people? By no means! I am an Israelite myself, a descendant of Abraham, from the tribe of Benjamin. 2 God did not reject his people, whom he foreknew. Don’t you know what Scripture says in the passage about Elijah—how he appealed to God against Israel:
That is in the new testament...I thought that should quench whatever argument.

Oh well....

Replacement theology (also known as supersessionism) essentially teaches that the church has replaced Israel in God’s plan. Adherents of replacement theology believe the Jews are no longer God’s chosen people, and God does not have specific future plans for the nation of Israel. Among the different views of the relationship between the church and Israel are the church has replaced Israel (replacement theology), the church is an expansion of Israel (covenant theology), or the church is completely different and distinct from Israel (dispensationalism/premillennialism).

Replacement theology teaches that the church is the replacement for Israel and that the many promises made to Israel in the Bible are fulfilled in the Christian church, not in Israel. The prophecies in Scripture concerning the blessing and restoration of Israel to the Promised Land are spiritualized or allegorized into promises of God’s blessing for the church. Major problems exist with this view, such as the continuing existence of the Jewish people throughout the centuries and especially with the revival of the modern state of Israel. If Israel has been condemned by God and there is no future for the Jewish nation, how do we explain the supernatural survival of the Jewish people over the past 2,000 years despite the many attempts to destroy them? How do we explain why and how Israel reappeared as a nation in the 20th century after not existing for 1,900 years?

well, that escalate quickly
on the other extreme side, we have Zionism Christian.

well
I believe in only one convenient, the one written with blood of jesus. if one reject jesus then God will reject him. because jesus is only way to God.

you mean there is salvation other than christ?

I figure you talk about what left of Jews at end of time will believe in God and be saved
but currently at present time, I don't think it is happening, ie Jews all believe in jesus

in other word, they are still rebellious against God at current stage and their heart is hardened
is that right?

Basically they consider it as 'do not brag about your salvation because it came from the "root"'
I guess during that time, the reformers were fighting the grace war with catholics. The focus wasnt there to properly develop eschatology I suppose?

Faith doesn't demand anything. Faith doesn't coerce, doesn't obligates, doesn't force, doesn't threaten - a person to do any work. Faith simply creates a desire, or a suggestion, that a person should do the right work. But our flesh also does the same thing. Often times, when faith suggest something that we should do, our flesh will suggest an opposing work. So we are always left with two choices, to follow the desire of faith or to follow the desire of flesh.

For example, when I see a man lying injured on a remote road, my faith will suggest me to help that man. But at the same time my flesh will also tell me to run away because my flesh will often provides a supporting logic as to why I should run away. Maybe that man is faking it, or maybe he is a bait, and there are some bandits hiding and waiting to ambush me while I am helping the man.

So this is the common battle between faith vs flesh in our conscience throughout our daily activities.

Most christians like me are more incline to follow the flesh rather than faith. If I am able to reach 100% obedience to faith, and 0% obedience to flesh, then I can say that I have killed the flesh, that I have murdered the flesh, just like what Paul said. And I live in the Spirit, through faith alone, because my faith is strong and ALIVE and not dead as James explain it clearly in his book. So we should always "work out" (or exercise) our faith, because if we don't, our faith will eventually become dead as it will always going to lose to the flesh if we have no bias towards it.

No, if Abraham just believed without acting, Ishamael would not have been born. And because Abraham added work to his faith (by sleeping with Hagar), which was a mistake, the Arabs were born.

When we think that faith demands action, we start to plan action that we consider or reason it as good to God. This is not necessarily true. What we consider as good work might not be considered good by God. Eve thought that eating the fruit of knowledge was good, but her reasoning was flawed, and so does all of us who thought we know what is considered good work.

I wonder how does the wife feel? Her husband having sex with another woman and the wife ordered it.

So I am assuming you understand fully what you preach. Here is my question, do you think Jesus is a demanding God?

And, if I may ask another question, say we want to apply your theory in practical situations, what actions that a christian MUST DO for his faith?

I will humbly admit my knowledge regarding faith and action is quite limited. So I am learning right now as I ask.

Let your light so shine before men, that they may see your good works, and glorify your Father which is in heaven.

Hebrews 11 King James Version (KJV)
11 Now faith is the substance of things hoped for, the evidence of things not seen.
2 For by it the elders obtained a good report.
3 Through faith we understand that the worlds were framed by the word of God, so that things which are seen were not made of things which do appear.
4 By faith Abel offered unto God a more excellent sacrifice than Cain, by which he obtained witness that he was righteous, God testifying of his gifts: and by it he being dead yet speaketh.
5 By faith Enoch was translated that he should not see death; and was not found, because God had translated him: for before his translation he had this testimony, that he pleased God.
6 But without faith it is impossible to please him: for he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him.
7 By faith Noah, being warned of God of things not seen as yet, moved with fear, prepared an ark to the saving of his house; by the which he condemned the world, and became heir of the righteousness which is by faith.
8 By faith Abraham, when he was called to go out into a place which he should after receive for an inheritance, obeyed; and he went out, not knowing whither he went.
9 By faith he sojourned in the land of promise, as in a strange country, dwelling in tabernacles with Isaac and Jacob, the heirs with him of the same promise:
10 For he looked for a city which hath foundations, whose builder and maker is God.
11 Through faith also Sara herself received strength to conceive seed, and was delivered of a child when she was past age, because she judged him faithful who had promised.

23 By faith Moses, when he was born, was hid three months of his parents, because they saw he was a proper child; and they were not afraid of the king's commandment.
24 By faith Moses, when he was come to years, refused to be called the son of Pharaoh's daughter;
25 Choosing rather to suffer affliction with the people of God, than to enjoy the pleasures of sin for a season;

30 By faith the walls of Jericho fell down, after they were compassed about seven days.
31 By faith the harlot Rahab perished not with them that believed not, when she had received the spies with peace.
32 And what shall I more say? for the time would fail me to tell of Gedeon, and of Barak, and of Samson, and of Jephthae; of David also, and Samuel, and of the prophets:

You realize something? In the Hall of Faith (Hebrews 11) even though Abraham lied twice and Sarah laugh at God for doubting on the birth of Isaac, their flaws were not recorded but instead were given praise for their faith in God.

In your faith demands action theory, what kind of action are you talking here? Man's work or God's work?

In John 15
5 I am the vine; you are the branches. If you remain in me and I in you, you will bear much fruit; apart from me you can do nothing.

Clearly Jesus said we cannot do any action without God. Basically it is God who is responsible for the action. Why do we want to take credit and strip God of His Glory by saying it is our action? God made the promise to Abraham that He would create Isaac, there was no condition from Him that He would fail if Abraham did not do anything. Even without men's contribution, God's Grace will still work.

So why then do you want to insist that Faith demands work, which can be elaborated as Faith demands God's work? Is it not like turning God into our servant?

What about Romans 4
5 However, to the one who does not work but trusts God who justifies the ungodly, their faith is credited as righteousness.

That verse doesn't speak of Faith demands action, but rather Faith demands Trust. Yes, Jesus is a demanding God. But what He demands is not of our works, but us to trust Him, to lean on Him, and to let Him do the Work. It is never about our own work at all.

Romans 3

27 Where is boasting then? It is excluded. By what law? of works? Nay: but by the law of faith.
28 Therefore we conclude that a man is justified by faith without the deeds of the law.
29 Is he the God of the Jews only? is he not also of the Gentiles? Yes, of the Gentiles also:
30 Seeing it is one God, which shall justify the circumcision by faith, and uncircumcision through faith.
31 Do we then make void the law through faith? God forbid: yea, we establish the law.

4 What shall we say then that Abraham our father, as pertaining to the flesh, hath found?
2 For if Abraham were justified by works, he hath whereof to glory; but not before God.
3 For what saith the scripture? Abraham believed God, and it was counted unto him for righteousness.
4 Now to him that worketh is the reward not reckoned of grace, but of debt.
5 But to him that worketh not, but believeth on him that justifieth the ungodly, his faith is counted for righteousness.

well, I see it as demonstration of god's perfection by the faith of crippled person. it can be said that work and faith is the two side of same coin. you cant separate good work from genuine faith
this is being plainly detailed by book of james.
no one think justification need work. but genuine and active faith must demonstrate good work / bear fruits.