Overview
Developer Mode is sort of 'cheating' on Halo: CE. It enables someone two totally pown AI opponents in SP maps, or it allows a map designer to test out a map they just created.
Alldev
Alldev is devmode that works for Halo: CE multiplayer. It allows hosts to basically cheat. Non-hosts can use the lesser cheats, but cheats such as invincibility can only be achieved by the host.
In order to get Alldev, you have to download it.
Other
coming soon...