After the rank captain and captain grades 1, 2 and 3 is Major
you need to be the rank of captain
After the rank captain and captain grades 1, 2 and 3 is Major
Captain
Just play and play till you get to Captain.
The fastest way to rank up is to boost in campaign. Search "halo reach campaign boosting" on youtube =)
Warrant Officer Grade 3
Just play a lot of campain.
You have to be an warrant officer in halo reach to unlock the helmet you also have to go to halowaypoint and unlock the armor.
It's a Chest armor unlocked at Captain (either that or major).
Halo reach is older
no, Masterchief is not in Halo: Reach. Halo: Reach is set before the discovery of Halo, if you have or Know about the Halo book: The Fall of Reach, it is a closer view of the plant reach. but there are some other Spartans in it!
over 1,000,000 credits by the way, its called CREDITS