Fake iPhone updates

What do you mean a fake update? There's no such things as fake updates.

All updates are pushed by Apple directly, and there's no way for any one to push an update to a device outside of the Apple servers. So no chance of an actual update being fake.

If he did something to the iPhone you are going to have to explain what it was. It was definitely not a fake update.

Did he maybe update to iOS 14 Beta? Its not a fake update, its just a testing phase update, which is expected to have issues.

Normally a restore should fix most issues you may encounter. Including removing any potential jailbreaks if that is what he did. Jailbreaking is not an update.

You can try to restore it following the steps here: Restore your iPhone, iPad, or iPod to factory settings - Apple Support

So basically he jail broke it

Use a computer to restore to factory settings by DFU mode

I would not recommend backup snd restore so assume all data will be lost

Use this process

If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support