Everything Rocky said is correct, and i'd also like to add a small sidenote:
Vegeta said that Frieza uses his first form to conserve energy, and later in the series, Goku says that SSJ3 is a lot easier in the Otherworld because less energy is used when transforming. HFIL/HELL is a part of the Otherworld and therefore Frieza loses no energy and can remain in his Fourth Form for as long as he likes. I think the only reason he doesn't stay at 100% is because it puts a lot of strain on his body and slows him down.
On the subject, I think he should be able to descend as it helps get PL later on in the game and Frieza isn't overpowered or anything so there's no reason why he shouldn't be allowed to do this. Also, it's true to the show which i'm all for :yes: