Some people did have requests denied. In my org, every single person who applied was approved. It is easy to change teams at google, so people who really want to work remotely can make it happen.

It totally depends on where you're living. It could even be a salary increase if you were previously working in a lower CoL office but have since moved to a high CoL region -- in that case your salary would increase. There's definitely no blanket single figure that applies (in either direction) to people who go fully remote.

E.g. my grand-boss is a fully remote worker based out of Manhattan. He's getting the highest pay tier.