I've tried both with no luck.Try tapping F2 as soon as you turn it on. That should take you into the BIOS. If that doesn't work try the delete key.
In my opinion, it shouldn't be this easy to bung up a system in the first place. Yeah, I'm kicking myself for changing the UEFI setting to Legacy, but I'm also kind of pissed off that Acer didn't make a more failsafe setup. Mere setting changes in bios shouldn't cause irreversible shit like this to occur, in my opinion.