Yes
yes
it is for messing around if your normal halo 3 gets damaged.
halo 3 is second best but girls definitely come first.
By getting halo 3 odst ( two discs ) first disc halo 3 odst campaign and 2nd disc halo 3 mythic comes with all the halo 3 maps.
halo 3 ODST will probably come with a second disc with all the Halo 3 Online maps on it (all 21) plus 3 more. will be halo 3 format.
It is not on a disc! It is on the sheet that says Halo Reach, But you will need Xbox Live.
Halo 1 first came out on November 15th, 2001.
halo reach come before halo combat evolved
Yes and no The achievements will be counted the same and so will the disks but if you have the ODST multiplayer disc (Halo 3 Mythic) and you join someone's campaighn on regular Halo 3 it won't work same thing if someone on HAlo 3 regular joins a map that comes with ODST for example SandBox.
2001
Halo is xbox only but the first and second work on the 360 as well.
Yes.