It depends, many popular original Xbox games are compatible with Xbox 360 to check this out you should visit http://www.xbox.com/en-US/games/backwardcompatibilitygameslist.htm
yes
Well first you need to go to Gamestop and see if they have the game their for xbox. Then before you buy it, you want to make sure the price sticker has a DC on it which means you can play the game on Xbox360. But just a waring, you need a special type of update disc to play the xbox game on the xbox 360.
If your just gonna use the 2 regular xbox's to link up. Your gonna need a System Link Cable. If you go to your local geek store, just tell them you need a crossover cable. You can eliminate all that if you have a hub, or a router. Then you could just use regular Ethernet cables. A System Link Cable (crossover cable) Is the cheapest way to go. Make sure you get a long enough cable to reach both ethernet jacks on the back of both Xbox's. You also need the same game in each console. And it has to be a linkable game.
If you need more memory hardware you can buy a chip from the nearest game shop and it will just slit into your xbox console.
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).
if it is a Normal Xbox game and you want to play it on the xbox you may need to manually update your xbox
You will need to mod your Xbox 360.
There isn't a way to mod Halo for the XBox. You'll need the actual computer game to do this. Yes you can mod halo for the Xbox but you need an action replay memory card and the original Splinter Cell game and that's basically all I know just google it and you'll find something on how to do it. You will need special tools found in off color irc channels. You will also need, as was stated by previous person, a modified XBOX, but, it can be done both the way suggested or using what is known as a Mod Chip.
yes you can you need to for it to work
No, Xbox Live is Microsoft's content and community service. You do not need Xbox Live in order to play any Xbox game.
go to a game or game staion and ask someone how to fix it or just ask for a refund for it but you will need a reseat as well
First you need a hard drive or a memory unit then when playing a game check in-game instructions.