you have to complete Halo 3 odst on legendary, have xbox live and complete halo 3 on legendary
No, only elite's.
There is no Brute armor in Halo 3, only Elite and Spartan models.
You unlock the armor.
go to http://hubpages.com/hub/Halo-3-Armor
You unlock the odst armor by unlocking the UNSC SPARTAN achievement
you have to get 49+ acheivments
There isn't a known cheat code for this on Halo 3.
You have to complet the game on legendary
Get some skulls dummy
yes you still unlock the armor. you and the player that your playing with unlock the armor. =] =) =p q=].
there is no permanent cheats in halo 3. you need to unlock them by achievments. and, you can not get the flaming armor effect, it is only for bungie employees. in halo reach, buy the legendary package to get that armor effect.
I'm afraid that you cannot be a brute in halo 3.