-False, Accele actually boosts all mp gained that turn if you use an Accele disk first. IIRC it even makes Blast discs give a little bit.
-True, charge is just charge. Fun fact:Puella combo charge does the same damage as puella accele.
-False, you can and it's REALLY strong, especially in mirrors (where all discs are 0.2 base power stronger, so blast discs are proportionately stronger overall). Watch as Tart one-shots an entire team at once with her puella BBB
-True, although according to the wiki Magia actually boost other magias used after them in the same turn???
So, followup attack basically gives the character a Chaser attack. So for example, ideally, you want to use Renconnect->Ren disc->Ren disc for a puella combo where the person she connects to follows up both the second and third disc. (But it still works when anyone else attacks either, just Ren discs give a puella combo) So with Ren's connect, you actually DON'T want give the person she connects to more discs that turn.