In all the times I've played this game, I've always been a card hoarder, NEVER refining my rares until endgame – maybe once I've turned Minotaur into Adamantines for an early Lionheart, but usually I wait until you can get them from Adamantoises instead. However, this time, I want to go ahead and refine Siren for 3 St-Atk-J's. My questions are:

All GFs learn a full slate of 22 abilities. If I use an item to add a 23rd ability, what happens when their usual 22nd ability is supposed to be learned? Does it never show up? If I go back later and delete an ability with Amnesia Greens, will the blocked one reappear?