It depends on what you call beat. To Complete Halo you should complete All 9 Campaign missions, Some people also may want to try it on harder difficulty levels.
yes
wait for the next halo
Yes
Yes
yes his account is iPhLoXiTy and he beat every halo pro in Orlando
beat the campaign on heroic(might as well beat it on legendary),and go on halo waypoint(u need xbox live)
Follow the objectives
Definitely.
The whole army of Halo would beat Iron Man,but Iron Man can beat master chief because he has better thecnology.
no
With time and patience. Your not specific enougj
Beat the game on legendary