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Will achievements in halo 3 odst count towards halo reach such as armor

Will achievements in halo 3 odst count towards halo reach such as armor
Maybe. You will have to go to Halo Waypoint as that is the only other place besides the Armory in Reach that has any varients. also you must unlock acheivments like beating Halo 3 on Legendary to unlock a special helmet etc.