Board Thread:General Discussion/@comment-25597861-20150210170713/@comment-25355646-20150210181635

Zelena can't come back. The magic seen at the end of 3x20 was not Zelena, it was her magical essence manifested. In the fourth episode of OUaTiW Jafar talks about how someone born with magic has within them something called a magical essence, but he was able to control Amara's through that potion he mixed in her wine. The pendant that Zelena wore had the ability to hold her magic within it and amplify it and the pendant was connected to Zelena. So when she died, the magic that was being held within the pendant was released ("had no tether" as Regina said) and it performed the last thing Zelena was trying to do before her pendant was taken from her, which was open the time portal.

As for the spell that contains Maleficent, Regina cast the spell but we don't know if it origanlly was Maleficent's or not. There were three people that Regina loved (not counting Daniel): Henry Sr., Cora, and Maleficent. Regina wanted to make sure she wouldn't have any weakness after she cast the Dark Curse because "love is weakness" to her. So, Regina sent Hook to kill Cora, she killed Henry Sr., and she didn't want to let go of her only friend so when she casts the Dark Curse, Regina must have tinkered with the curse so that Maleficent would end up in a different form trapped underneath the clock tower. This means that Regina loved Maleficent more than Cora.

Sorry for the long post. But I hope this helps.