You need all maps( Heroic, legendary, and mythic) to play on the playlist cold storage is optional but not needed.
it should be since the multi player is the same but u can always find it in the game marketplace under halo 3
If by "halo 3 maps" you mean the Halo 3 Heroic, Legendary, Mythic and Cold Storage maps, then yes. However to play campaign levels, you must actually advance in the game to get to them.
you probaly need legendary, cold storage and/or the heroic map pack.
it depends if you have halo Reach, 3 or ODST. but if you have Reach you should just have to select it from your hard drive storage and play it. To get the gamemode it usually comes with the map.
In order to unlock all of the halo 3 maps you must purchase them from the halo 3 marketplace... heroic map pack is free, cold storage is free, and legendary map pack is about 600 live points...
halo 3 obviously
Halo 3: ODST is the newest of the two, but not the newest Halo game.
The halo time line goes Halo Wars, Halo: Reach, Halo:CE (halo 1), Halo 2, Halo: ODST, Halo 3. Halo 3 and ODST are practically at the same time.
Halo 3 ODST is not for PC but Halo 1 and maybe Halo 2-3 are
After Halo 3 there was halo wars, halo 3 ODST, and Halo reach. A new company (not Bungie) will be making a Halo 4 and rumor has it there will be a remake of Halo Combat Evolved.
it goes halo, halo 2, halo 3, halo 3 odst and soon halo reach will be available
No.