re: If Osweiller gets off the bench at halftime and wins super bowl 50,

It's the last game of his career (likely) and it's the Super Bowl, unless Peyton is carted off the field on a stretcher the only way Osweiler sees the field is in practice reps. But the answer to your hypothetical is yes, Tom Brady was a 2002 AFC champion even though Bledsoe came off the bench and played most of the AFC championship game