1000 gamerpoints gives you the katana, not the security armour.
you gut some
Nope.
No, you will not. All gamerpoints earned will stay the same. No matter if you were offline or online its on the profile.
nothing there gust thing to collect like stamps
No. (360)
Unfortunately, gamerpoints can't be transferred from one account to another, even if you move the save file.
No, gamerpoints are gained by doing achievements. that's the whole purpose of a gamer score it is used to show how much achievement you have done and how hard to do that achivement by gamerscore
No, the only thing that'll change is your gamertag.
Achievements are certain tasks you can complete in each game. Getting an achievement (called "unlocking" it) awards you with gamerpoints. You can't use these to purchase anything, but they generally serve as an indicator of how good you are at a game, or how much of a gamer you are. Someone with low gamerpoints is either new or doesn't play many video games, whereas someone with many gamerpoints probably spends most of their time gaming. Most games on a CD have a total of 1000 gamerpoints to earn, and most game add-ons and arcade games have 200 points to earn. You don't need to earn them all, they don't affect gameplay.
Most map packs are 800 Gamerpoints and need to be purchased via XBOX LIVE. Sometimes, there are discs out there for sale, but I highly doubt there are any for Halo 3. There used to be for Halo 2 though. Bottom line: Purchase from XBOX LIVE for 800 Gamerpoints. (Except Cold Storage, that one is free!!!!)
avatar: legend of angg the burning earth. seriously it takes about two minutes for 1000 gamerpoints :)