Can I install disc 2 on another console?

Can I install my multiplayer disc (Disc 2) on a friend’s console, as well? He wants to try Halo out before he gets it to see if he likes it.

Sure, why not?

Yup. You need disc one to access it though,

Yes you can, but he can’t just install disc 2 and play multiplayer.
Disc 2 is just an install disc, and he will need disc 1 to access the content.

Like others have said Disc 1 would also be needed.