you cant
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.
Yep.
muythic map pack. that comes with HALO 3: ODST
ODST does'nt have the AR.
Yes.
The Arbiter does not make an appearance in Halo 3: ODST.
in HALO 3 you are a Spartan and in HALO 3 ODST you are a Orbital Drop Strike Trooper (ODST)
On Kilowani Station. Which is the final clue.
yes only multiplayer has the new map packs but you can get them in the DLC
Yes. There are at least two more. One is Halo 3: ODST, which is an FPS starring and ODST (it will also come with every multiplayer map from Halo 3.) The second is Halo: Reach, which nobody knows much about. Look for a preview in ODST.
Halo 3: ODST will only be released on the Xbox 360. The are currently no plans to make Halo 3 or Halo 3: ODST available on any other console other than Xbox 360.