I’m leaning towards the “imposter” theory, but I don’t think it’s Cora and Hook.
Cora can shapeshift, Hook cannot.
Cora knows Henry’s name and his relationship to Emma
Cora saw Emma and Snow’s tearful reunion and daughter and mother, so she understands their relationship enough to be believable as Emma.
Ergo – Cora shapeshifted into Emma, Snow doesn’t know it’s not Emma. Snow and “fake” Emma got back to SB with Charming’s help.
Emma is still in FTL with Hook, both knowing the truth and trying to figure out how to get to SB.
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