Mutants are the same as alicesIt just so happens that Values Dissonance causes mutants/alices to be looked down on the the United States, while mutants/alices are respected in Japan. Also Z (the Anti-Alice Organization) is a branch of The Brotherhood of Evil Mutants, or vice versa.
Yuu Tobita is Stepford Smiler.Everyone has at some point been revealed to have some angsty part of their past, except him. Once, during the Alice Festival arc, when he was making illusions for the haunted house, some of the characters wondered what "goes on behind his innocent face". Therefore, when and if some angsty part of backstory is ever revealed, he will be revealed to be a stepford smiler.
Sumire is being controlled by Luca.Think about how their Alices interact.
When Nodachi took them back into the past, they came back in child form to Alice academy, which was where Hotaru and her brother was waiting all those years.And they relived their student years, starting from the point where the ESP died. Screw stable time loop, this way, everyone's got a happy ending.