If you are NPQ can you walk away from the contract?
"It depends."
After your freshman year (someone please correct me if I'm remembering incorrectly), you sign your contract of obligation. If, along the way, you become NPQ from the Navy, you're out, no questions asked. If you become NPQ from aviation, then you're still "in-play" and will place you into a compatible designator (SWO, RL, etc). If you don't want that and quit, expect that the Navy will want some payback.
After you commission, the Navy owns you (for a while), so they'll send you where they need to to meet your commitment.