Originally Posted by
e-aviation
Related to this, if I redeem a hotel stay, and then upgrade with cash, is it counted as a stay for status?
No, you will not get night or stay credit as your stay is still considered an award stay.
With that said, sometimes mistakes happen and you might get lucky. So while it is possible to get a stay or night credit when you upgrade an award stay with cash, it just isn't normal or part of the rules.