No you can only play mw3 on xbox 360 (and pc and ps3 of course) not on xbox.
you absolutly can't
Yes, you just have to pay for them, if you have elite, you get them early and free
You cannot play infection on mw3 wii version. But people found it by hacking.
Play more and read the wiki on MW3
it is currently under the community playlist online so have fun. :)
No.
You can't play.
Probably not
Yes you can.
yes of coarse
mw3 is awesome very awesome for awesome people and this stupid tf2, the gun suck, everything in tf2 is suckish. play mw3, mw3 is the best and tf2 are for noobs and losers