Yeah, you need a hard drive to play firefight with someone, if your doing it solo that's fine but in matchmaking you will need it regardless.
You do need a hard drive to download expansions, but the system won't turn on if you don't have a hard drive, so if you can turn it on without problems, and can play games then you definitely have a hard drive and you are able to download expansions.
yes the normal x box and kinetic are the same thing only one is sleeker and has the built in 250 GB hard drive.
Yes and no The achievements will be counted the same and so will the disks but if you have the ODST multiplayer disc (Halo 3 Mythic) and you join someone's campaighn on regular Halo 3 it won't work same thing if someone on HAlo 3 regular joins a map that comes with ODST for example SandBox.
put it into your computer then download them onto your hard drive then download it onto your card
yes
NO, you need a flash drive for everything.
you need an xbox hard drive
You can install Halo Reach to your hard drive like any other Xbox 360 game, however the game must be in the disk drive in order to play the game.(but if you have to put the disk its a waste of time to installing it)
yes
No, that would be silly.
no but you need a hard drive to view films in threatre
yes
it depends if you have halo Reach, 3 or ODST. but if you have Reach you should just have to select it from your hard drive storage and play it. To get the gamemode it usually comes with the map.
the armour will be on the hard drive of who ever put in the code eg. if you do it will be put on your hard drive. your brother could use the armour but only if he was using your hard drive as the download only works once.
Yes you do and you also need an Xbox LIVE account.
Yes of course it dose.