How can I remove my hotspot from someone else’s device after sharing it?

There’s no way for YOU to change or delete the WiFi settings on THEIR device.

However, changing your Hotspot password WILL prevent them from accessing your hotspot going forward. (assuming that it’s long and complex, not easily guessed, or derivable from your prior password)

You can safely change your phone’s name to anything you desire - including the prior name.

Your privacy and security concerns are well placed; I’m guessing that you’ll probably be more wary if asked to do this again.

However changing the Hotspot’s password — in addition to simply leaving the hotspot “off” when YOU aren’t using it — are really all that’s available and necessary.

They might still see the hotspot name if you're nearby and it's on, but without the correct password, they can’t join. No further privacy or security risk there.