Was it a plot flaw 또는 did I miss something?

That confused me too. Jefferson had worked for Regina before but it seems like he had never taken her to Wonderland prior and yet she's obviously been there before. Maybe there's another way to get to Wonderland, perhaps down a rabbit hole?

The writers did say Wonderland would leave us with a lot of 질문 so maybe it was intentional? Not sure.

Well i really don't know how to answer but the 퀸 of hearts is Cora because remember when Regina pushed in that mirror i think that's why? I hope that helps.