Ps4 need psn plus account to play online multi players games.RM127 is annual fee for psn plus.

Ps3 no need  psn plus account to play online multi players.

1. Correct
2. Correct

monthly, 1-3 games, depends...seriously, in my opinion, just get the PSN Plus, it's really worth it. I don't own a PS4 (yet  ), I just have a PS Vita and even with that, I feel it's more than worth it 

BTW, PSN Plus will give you free monthly games for all 3 platforms, PS3, PS4 and PS Vita, great if you have all 3! 

us psn give quite a number of good games. But dont rely on that much for ps4. due to limited number of games right now, dont expect killzone or need for speed or any disc based launch title to be free anytime soon. But one can always hope, right....

yes, depends on which region of PSN+ you subscribed to, but mostly will give in that range.

for US PSN, you can refer here for updates, http://blog.us.playstation.com

Once u've claimed d free ps+ game! it can b played until the validity subscription of ur ps+

Once u've claimed d free ps+ game! it can b played until the validity subscription of ur ps+

PlayStation®Plus
FAQs

Q:How long do I get to keep the games in Instant Game Collection™?
Games in Instant Game Collection™ are free to download with a Plus membership. As long as you're a PlayStation®Plus member, you'll always have access to any game you've downloaded in the collection, even if you've deleted a game from your hard drive previously.

Q:What happens to the games and DLC I downloaded through a PlayStation®Plus membership and I decide to not renew my membership?
You will not be able to access free games downloaded with PlayStation®Plus if you choose not to renew your membership. Any item you paid for is yours to keep. Once you decide to re-activate your membership, you will once again be able to play all games downloaded from Instant Game Collection™.

Q:When does new content rotate into Instant Game Collection™?
At this time, we add new games to the collection several times a month. This could change and we're always looking at the best way for gamers to experience PlayStation®Plus.

Q:If a game rotates out of the collection, can I still download it free with my Plus membership?
If you did not download the game when it was in the collection, you will not be able to secure your free download. However, if you downloaded when it was in the collection, but it's no longer on your hard drive, you can visit the PlayStation®Store and re-download it anytime, as long as you're a member.

Q:How many times can I download / re-download a game in Instant Game Collection™?
You can download a game as many times as you like, even if it's been deleted from your hard drive, as long as you're a PlayStation®Plus member.

Q:If I buy discounted content with my Plus membership, will I lose that content if my membership expires?
Content that you purchase with a discount as a Plus member is yours to keep, regardless of your membership status.

Q:I’m already a PS Plus member. Do I need to buy a separate membership to get Plus on the PS4™, PS3™, or PS Vita systems?
We’re happy to say that it’s one Plus membership to access all Plus benefits across these three devices. It’s not simply an introductory offer, it’s the way it is as far as Plus access on the PS4™, PS3™ and PS Vita systems.
http://us.playstation.com/playstation-plus-new/