nope
yes you have to have steam.
A person can play L4D in L4D2 in PC by selecting a player and joining a game. Most of the game itself is very similar to the original release other than the characters and maps.
yes vs is the main mode also from next week you can play realism vs
l4d2 it has more zombies and its more funner.
Yes but only with split screen
You can hack it on to your xbox. I do not know the means to do so however. I am looking right now for it
Depending on which platform, (hopefully through steam) online play for all games should be free. This should be true for Xbox games as well, though Im not too sure on it. If your planning to get L4D2 on PC, buy it through steam and you should be set for unlimited online play! (Internet required)
yes
Yes, Download steam, make an account, search L4D2 and download the demo from there.
You can play either one you want, they're standalone games.
I have l4d, Not l4d2. But, there is no specific order. They're all different stories with the same people involved.