they dont have a firefight demo for halo reach soz
You can't only in Halo Reach Firefight.
No
it depends on your firefight settings, and your skill.
no
yes but you can play matchmakeing firefight on your own
In the wave options when customizing a firefight game.
yes
They only work in firefight. Also, they happen automatically in firefight
It is called active camo in Halo Reach, you can find it on loadout screens in firefight and matchmaking.
Magnum
by playing campaign, firefight, or matchmaking