depends on your skill
you buy them on xbl marketplace, it has nothing to do with beating it.
You get it by beating the halo 3 campain on legendary 9 times
when get achievements (like beating the game on Legendary or finding all the skulls) you can unlock some of the armor.
I don't think that Halo 3: Legendary Edition is a game.
you have to complete halo 3 odst on legendary, have xbox live and complete halo 3 on legendary
You do not have to do them in order, but you must complete them all on heroic (or legendary) to get the acheivement.
beating the campaigne on legendary is a fast way of unlocking most the armor. some achievemnets also unlocks armor.
Yes. As long as you beat each level at some point at heroic difficulty or higher(legendary).
It does not come with Halo: Combat Evolved or Halo 2.
Depends on what level You beat it on.
You may have missed a level. Double check and if not it may have not done the levels all on legendary. Or you may have completed the game on legendary with a friend and not on your own!
The halo 3 legendary edition is one of the editions of Halo 3, those being Halo 3 Standard Edition, Halo 3 Limited Edition, and Halo 3 Legendary Edition. The Legendary Edition comes with the game itself, a model of a spartan helmet, (the main character, Master Chief, is a spartan) although it can't be worn. It also comes with a poster, and 2 DVDs which have a lot of content.