So Hunt tests, you can PICK who makes them, but the majority of people who attempt the test must pass for the hunt to succeed?
Yeah, that's the way I read it.
And for Stealth tests, it says each adventurer MAY attempt a PER test, and if everyone passes, you increase the level by 1. Does that mean if someone chooses not to make the test, the stealth check has failed?
Yeah, it says every member of the party must pass; if someone doesn't check, they don't pass.