Halo 3 I'm guessing
Start, Right, Down, A. That'll give you the ability to change your color, armor, emblem etc.
No, it just looks awesome!
Halo 2 was made for the original xbox, unless there was a console before the "xbox" that I didn't know of. It looks cool on the 360 though and Halo 3 looks even beter.
If You Mean change into elite, no, you can only do that in Halo 2, 3 and Halo Reach. But however you can use mods at halomods.com
scout armor is only for looks
The armor is purely cosmetic. It's only for looks
the lobby in halo 3 and 1 are actually very different. the lobby looks better in halo 3 but i think its a bitt more complicated
It will change about when halo 4 comes out
Corona.
halo reach is the last halo game unless they change their minds
only in halo reach you can to that
you can customize your character in halo 3. and you can change your character that has different armor in halo 3:odst
it looks like a wasteland