You can but it requires a dongle and doesn’t work in most apps.

https://support.apple.com/guide/iphone/external-storage-devices-iph95baac91f/ios

No and they clearly could but then you wouldn’t need to buy them from the ringtone store. In other news, you can use any song as a custom alarm’s sound… but not your daily Sleep alarm.

I wish I’d known about the Siri command but the details/overview navigation option still exists. It’s toggled by tapping the button on the top-right of the screenshot shown on this support page: https://support.apple.com/guide/iphone/get-turn-by-turn-directions-iph215b053f6/ios