Hey, those are argente babies hahah... you view my sales thread lah, same colour as Andante I think.
A tame hamster would not bite on purpose. A tame hamster would not jump out of hands in an instant. A tame hamster would not struggle too much when held.
Hamster is like that mah. Animals do not think like humans nor do they have emotional feelings like humans. Since you always feed him, he see you as food source. Also hamsters have tiny brains compared to dogs and they are not monogamous.
Change colour? Hmmm.... that is really weird since got red eyes. I suspect the shop keeper mixbreed them. Again, many petshops do not know mixbreeding different species of hamsters is bad. Well, I can tell you lucky yours are ok. When I was younger, I bought hybrid hamsters before, damn weird and aggressive... and it was red eyed... change colour also.

Accidental nips are common lah. Part and parcel of owning a hamster hahahah.

Never let out a hamster freely. Really, it is worst loh when it gets lost. Normally the best is making a play pen using old cardboard boxes and make a maze for them to play. Or you can buy those hamster fencing sold at certain shops(I have been searching but can't find till now). Best is an open area like your bed but again your hamster must be tame in order to do this. For me, I let my hamsters run on my study table, that is why a few pics got stationary and keyboard hahaha...

Anyway, a hamster is happy enough if it has a wheel. Do not let it roam freely without you watching lah if you wanna let it out of the cage.
Why are they scared? Give you a scenario.... say you were small like a hamster, and a giant monster take you as a pet. You like? You of course scared rite? Then later you and monster also cannot communicate since got language barrier. At first you damn scared but when monster feed you, you suddenly realise got food and feel comfortable. Then all of the sudden the monster pick you up and molest you up in the air.... you also don't like rite? So it is the same with hamsters.

You gotta make them get used to you. Teach them that your hand is good and won't give pain. NEVER catch them out of their house. You are intruding into their safe haven which makes handtrusting worst than you started. Is like a stranger from the street came into your house, open your bed room door and drag you out into the road... same feeling lah.

Hello there! Welcome. Haha.. Don't worry. Hamsters are nocturnal. They sleep always during the day. At night? U sure you stayed up whole night to monitor them? They'll only be active with lights off. Mine are active from 3am - 8am. But if I wake up at 7am and off the lights, it'll go sleep first. Pet shops hamsters are much more timid. Not tamed yet. You need to spend more time with it. Be patient. Mine's been with me for 2 months alrd and yet it still won't let me catch it when it's in the cage. Outside of the cage it's fine. Give some time to your hamster. My older RC which I had(died) only learned to be nice with me after a year. Every hamster have different character.