De-Fusion can only target Fusion monsters. Ra is not a Fusion monster, so no, you cannot use it on Ra.

Yes, because it is a quickplay and can be activated during the battle phase.

Yes, De-Fusion is Quickplay so you can attack with the Fusion Monster, then use De-Fusion on it, and since it's still the battle phase, the newly summoned components can attack too.

Defusion - 2012 was released on:

USA: 22 November 2012 (video premiere)

The cast of Defusion - 2012 includes: Aeneas Middleton as Mr. Steinberg - Police Officer