Used to happen to me all the time.. the solution? Learn from it. There's no way to undo anything unless you load a save file. No reverse-time spells (for now anyway).
As for the backstabbing, if the cursor is close enough to a character, movement actions cost 0 AP. So it's just like turning, except... you're moving. But not actually spending AP.
Last edited by Nathan Jumalon; 12/01/15 06:38 PM.