Not until Halo 4 you can't. By the way, in Halo 4, you can FORGE a pelican! :D
Yes, there will be forge mode in Halo 4.
Yes, it will have forge
Yes, 343 Studios (The creators of Halo 4) have confirmed and showed a demo of the upcoming forge.
You cannot make your own maps in Halo: ODST, it doesn't contain forge world. Halo 3, Halo: Reach and Halo 4 all contain forge world.
You can download a mod for halo2 on xbox somewhere on www.keygens.nl. Then you have to get a net work cable and connect you computer to the xbox(there is a network port on the back of the xbox and on the back of the PC) and then you just drag and drop the mod on the xbox's hard drive and halo should recognise it and let you play forge.
Play locally.
The map "Forge World" in a Halo: Reach is just a large map with nothing on it, other than like trees and rocks and stuff. There are only 4 items which you can place in Forge mode on "Forge World". 3 of which are in the spawn category.
First, You go to the menu then find file browser. you can search maps from there.Second, there is no second
Most likely in Forge, Custom games and Matchmaking. Campaign? NO
Spartan ops, forge, campaign, co-op multiplayer
You can't, but you can delete some pre-existing objects for more room.