You unlock milestones by getting achievements.
For your avatar go to halo wavponit and you should get one in your milestone check area.
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!
halo reach is the bomb
There are no skulls in Halo Reach.
Halo reach is older
chances are no their will not be a new halo after reach
No, there is no Hayabusa armor in Halo Reach.
you pre-order Halo reach
There will not be another Halo game after Reach.
You can download Halo Reach on the Xbox marketplace.
there are no assassination sprees in halo reach.
Yes, Halo: Reach will include Forge.