I have an Oculus Quest 2 - it's really not intended to be multi-user (even within a single household), which seems like a big miss.
The answer to both of those questions is: "hit the factory reset button in the Settings menu" which blows away any and all state. That's realistic for selling the device but not really for lending it.
https://www.oculus.com/blog/facebook-accounts-on-oculus/?loc...