Yes, it includes every map ever released for Halo 3. This includes, but is not limited to, the Heroic, Legendary, Mythic (1), and Mythic (2) map packs. Basically, you wasted your Microsoft Points.
No, they do not. You need a compatibility app/emulator/whatever-you-want-to-call it for the Xbox 360 so that it can have backwards compatibility to run Halo 1/2/whatever. Good luck finding it, though.
For all of the people who are trying to run this application and cannot find the link to the newest DirectX, you can install [THIS] to update your computer to the newest version of DirectX.