Why All for One didnt keep a regeneration quirk for himself?
When All for One first appears in the manga in chapter 59, he talks about, how he wished to have gotten the regeneration quirk sooner (it probably took a long time to get that quirk, since it is so rare), because his wounds had already healed at the time, when he finally got his hands on it. So for those injuries, which had been caused by All Might, the quirk was useless. 

But it doesn't say anywhere in the manga, that he doesn't still have it. So, it is very likely, that he still has it and uses it for new injuries.