I don’t think they can stop the clock, meaning stop the aging, because it causes all sorts of problems for the child characters in the show who will get older and change and they need to allow that to happen on screen.
I think everyone will retain their memories because i know i would find it disappointing if they reset all of the character growth we had this season, but just had Emma believe. I would feel like haven’t we done this before. And they have a great place to move to. They can have all of these reintroductions with Emma getting to know her parents now that she knows who they are and they know themselves which is what i want to see. I want those scenes and not some sort of reset where Emma is meeting and becoming friends with Mary all over again.
They just need to move forward, in my opinion, and not back.