Even in her wheelchair, Olivia Benedetto dreams of backflips and handstands, tasks that were once as easy as jumping rope or climbing stairs. The aspiring gymnast still has the videos on her cell phone: Olivia doing a cartwheel, Olivia on the trampoline, Olivia perfecting her bridge. Sadly, the 13-year-old Queens girl has the other video, too, the one from three months ago when she was skiing ...