Guided access covers some of that, but I really don't think it's the whole story. Rather than locking everything to a single app, I'd rather something more like a guest session that sees all the apps, just all of them in a logged-out state... no messages, no emails, no calendar, no banking info, no history for Google Maps or open tabs/autocomplete in the browser, none of it.

But perhaps that feature is really just a subset of the broader users/profiles request that is being made here, because then I could have separate users for "primary" and "family" on my phone, and the "family" user would still enjoy continuity from session to session (game progress, previously visited YouTube videos, whatever) but in a separate universe from the continuity of the primary user.