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!
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.
You cant on AC2, but when Assassins Creed Brotherhood is released, you can then. :)
play assassins creed to find out
no it does not have online play
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, but I would suggest playing AC2 before playing AC Brotherhood if you care about the plotline.
Yes
Ubisoft
The Kenways
there is no demo
Yes, you can.