You can find the Unknown Sources installs from the Apps menu, using the
drop-down at the top right. See this screenshot (source:
If you used your FB account for your son's Quest 2, it should already be
connected to your account and the games will be installable from the
store as usual, perhaps I misunderstood the question? There is an App
Sharing/Multi Account feature work in ...
Your easiest option is just to reset the headset completely. Check which
games you played use cloud saves, the ones that didn't you won't be able
to backup simply. You mentioned you have SideQuest, do you also have
"Developer Mode" enabled? Perhaps y...