: 1. Can we play H:CE or H2 with new graphics and old sound effects?

No, they clearly wanted to separate new from old this time, so no mix matching.

: 2. Can we set our own callouts in H2:A forge?

Wasn't asked.

: 3. Will Breaking Benjamin and Incubus still be there when playing with old
: music?

Yes, legacy mode will have all old music and sound effects while Remastered mode has new music and sound effects.

: 4. Will campaign scoring be added for H:CE, H2, or H4?

Wasn't asked. but assuming that Frank said there would be no gameplay mechanic changes when someone asked about the weapon spawns in 4, don't count on it.

: 5. Will the Halo 2 Grunt Birthday Party skull be featured in it's original
: plasma grenade-y form?

There will be no gameplay mechanic changes, so yes?

: 6. Will campaign theater be added for H:CE, H2, or H4?

There will be no gameplay mechanic changes, so no.

: 7. Will H:CE campaign have rally points?

There will be no gameplay mechanic changes, so no.