1. Yep.
2. Dunno. I assume she always had it with her (because I also assume that Blue is not as innocent as everyone thinks and she had her memories the whole time the curse was in play)
3. Not sure. Bit of a plothole but maybe he used the globe that Gold left behind, as some have speculated. Or maybe he has a special Rumple-finding device of his own on board that ship? He got from Neverland to Fairytale Land to our Land in pursuit of his crocodile…. I think it’s safe to assume he hasn’t been led by Cora all the time. Otherwise, how would he know when to leave Neverland? He must have had something with him that would tell him when the time was right. Right???
4. They have history with Rumple. Probably more so than anyone else. Either they read it somewhere, or he told them (why, I have no idea why he would tell anyone about that) But others in the history we have seen have learned about the secret of the Dark One and the dagger…. surely legend spread, slowly but surely?