Selected contacts with this toggle’d on when they call it’ll simply ring overriding the silent/vibrate only mode.

There’s DND mode on Android however wouldn’t That mode also silence vibrations from everything but the exception list?

It deletes the app data after certain time… I’d say 15 mins.

I think it does this so you can resolve app glitches without having to reload your user data which could be game progress, app sign-on, etc.

I’ve fixed my YouTube app several times by deleting it and quickly redownloading it without having to re-authenticate.

Offload app selection is under General then iPhone Storage once the app is selected from that list