X-Box live.
Yes, Halo Wars is a Xbox Live game, therefore you can play online against other players.
I don't play Halo 2 on PC but my guess is that if it has campaign or story mode, you can play alone. If you wanna play multiplayer with other players, you can't unless you do local matches.
If you mean the Multiplayer disk that came with ODST then yes, but if you mean the ODST campaign disk then no.
Yes you can play both Halo: CE and Halo 2 multiplayer on PC.
There are matchmaking modes for multiplayer as well as firefight in Halo Reach. These would set you up to play with random players.
on an xbox press multiplayer
go to multiplayer
yes
yes you can be a arbiter in only campaign multiplayer
You change the play list in Multiplayer.
No, it does not, although some milder profanity is used. If you play the multiplayer mode online, you will likely hear other players use "the f-word," but you can mute their voices.
No you can't play multiplayer offline only single player. But you can play it online with other online players.