(1) There're 7 episodes for the pre-quel, they 
have all released.

(2) Pre-quel is CG, the old 6 episodes are made 
by cels as you know.

(3) Super Techno Arts (Studio APPP) tries to 
release it since last year, but they have been 
hitting the wall with different domestic 
partners.  I think they're now trying to bring it 
out by themselves.