No, not without a mod. But you can in the custom games when playing single player.
Same way as Halo 3
yes just check in youtube.com and look up how to lower weapon in halo 3 (i think)
You cant lower your weapon in multiplayer you can only do it when you change your network settings to local.
None of the Halo's have any 'real' cheats, the only one is the lower your weapon one, which is just like Halo 3's.
It's impossible, you can only lower weapons on local or system link
With a weapon in Halo 3
Dying
it is a halo weapon used in the games halo 3
Yes. The sentinal beam is a weapon.
Unfortunately, you have to have a weapon.
no there are no "cheats" in halo, thought many glitches
After finding a halo 3 skull, simply pick it up as you would any other weapon.