Yes you do
You can invite players to a game on xbox live whether or not they are playing the game. They must have the game (and an xbox live subscription) to actually join you and play the game, however.
There is no "The Xbox Live", Xbox live is simply a pay-to-play game service where you can play Xbox 360 games online. It depends on the game if you can play it online or not, the game's box should on the back say if it can be played online.
Yes. The only way to play a game with a single copy is to play on the same Xbox using a splitscreen multiplayer mode (if your game supports it).
You can not play DeadFrontier on xbox live, the game is stricly a computer game.
I don't think that you can play an original Xbox game on an Xbox 360 live. But some games from the old xbox you can play on Xbox 360.
It is based on the game and what is allowed with the game. You have to choose a game that allows it if you want to play online with a friend on your Xbox 360. The same answer does apply to the Wii and PS3
No, Xbox Live is Microsoft's content and community service. You do not need Xbox Live in order to play any Xbox game.
NO
if you have a hard drive you can play the xbox game's
Yes, you can play Halo 2 online on the Xbox 360 using Xbox Live.
You'll need a friend with you in real life, so you can share a screen. Your friend will have to add their controller, and then you can play. As for XBOX Live, split screen isn't needed as your playing on different consoles. Just invite them to an XBOX party and you can invite them to your minecraft game, no split screen needed.
No, Battlefield Bad Company 2 is not a cross platform game.