you need gold xbox live membership.
you don't.
Yes, but only if it is in matchmaking.
There are matchmaking modes for multiplayer as well as firefight in Halo Reach. These would set you up to play with random players.
Campaign should be one of three options to choose from when you first play Halo Reach. It will show up along with Matchmaking and Theater on the main menu.
yes simply go to multiplayer and it is the same set up as halo reach
Either get wifi or ethernet hooked up to your xbox and go into matchmaking or for two player offline just go to custom game.
You can't. In order to rank up, you need to raise your "highest skill level" and your "exp", which you can only do through matchmaking.
Infection is a game type. In custom games, simply change the game type to infection. Also, the "living dead" playlist on Xbox Live matchmaking only plays infection, so you can play there, too.
No. You have to play on ranked, or social matchmaking.
No, Halo Reach occurs much before Halo 4. In the timeline of the actual world, the games go: Halo Wars Halo: Reach Halo Combat Evolved (And Anniversary) Halo 2 Halo 3 Halo 3 ODST (Same time as Halo 3) Halo 4
two controlers and two profiles to sign in
Rank up to Lt.col in halo reach