I will be booking a backup flight in my daughter's name using my AA miles from LAX-BOS. I hope she doesn't have to use it lol - it's a positioning flight because she absolutely has to be in BOS on that day.

Will the miles come back to my AA account even if I input her AA number?

How do I know for sure that I can cancel and get my miles back?

How close to the takeoff time can I cancel if her regular flight works out?