Not certainly, but it would be a good story since the whole game is a trilogy. You should, I advice so that you fully understand the full story line of the game.
No
you do not need online to play assassins creed 2 on any game system, however if you are playing it on a PC it requires you to have a constant internet connection.
Steam is not a necessity for Assassins Creed 3. if you are speaking of online play then you will need to buy an online UPlay pass if one did not come with your game. Hope this helps!
Yes. There are more weapons, scenarios, and extra features to play with. I found Assassins Creed (1) Repetitive.
You cant on AC2, but when Assassins Creed Brotherhood is released, you can then. :)
play assassins creed to find out
Yes, if u don't beat assassins creed 2 then you will be totally lost when you play assassins creed brotherhood. because it starts off exactly where it ended and you'll be sooo confused of who everyone is how this all started what happened I HIGHLY recommended you play assassins creed 2 before you play assassins creed brotherhood. :)))
no it does not have online play
No, but I would suggest playing AC2 before playing AC Brotherhood if you care about the plotline.
Yes
Assassins creed 4 is an actual game for the PS Vita
Yes, it depends on what games console you have it on. For example: If you have it on the XBOX 360 you have to have XBOX live.