All of you complaining about it's gender...
I've taken many looks at the anime clips, aswell as this manga and determined that this is a new Mewtwo.
When we take into consideration the reading order, the scientists (which also are blasted in the window by genesect!! HINT HINT), and Mewtwo's actions in the manga, this mewtwo was created as a clone. There have been many attempts at cloning Mewtwo in the canons so I don't see why you people are so angry about the possibility of another one. There have been many mewtwos before, and you zoom in on this one because of it's gender? And don't say that's not a reason because I see so many sexist comments it's mindblowing, where did you get your people skills guys? >8U
"It's legendary and a powerhouse! IT CAN'T BE FEMALE" Oh okay so you're telling me out of the female versions of legendary Pokemon, a cloned Mewtwo can't be one of em?
But anyway, in that manga, it seems this new clone was scared upon first opening it's eyes and fled. Then possibly later returns because she finally learned a few things or two about life. If you paid attention to the panels - Dr.Fuji is not there, and it is not the same lab as before - thus, we can take into thought that this is not the same Mewtwo Ash knows. As if that wasn't implied already. I like this idea though, perhaps it will give us a legendary breeding mechanic in X and Y.
As for Sylveon's type.
I put together a lot of factors about it and determined it's either Bug or Poison type. c'B but that's just my findings (Nympheas. Look em up. They also have an alternate with Sylph in it, mostly all poisonous flowers, they're even seen in the background of the movie!)