How can I reset a bypassed iPhone safely?

If your iPhone is locked with a passcode, then no. In order to factory reset your iPhone, you need to access your iPhone's Settings menu.

If you have forgotten your iPhone's passcode, you can reset it using Finder on a Mac or iTunes on Windows. However, you will still need to enter the passcode for the Apple Account associated with the phone (if any).

You can see how to perform a restore via computer here:

If you forgot your iPhone passcode or your iPhone is disabled - Apple Support

If by "bypassed" you mean jailbroken or otherwise "hacked", we can't help you. That device is unsupportable.

you mean like this

Reset iPhone settings to their defaults - Apple Support

?

What exactly do you mean by “bypassed iPhone”. That term makes no sense in these forums. Is it a used iPhone you bought from someone? Did you find it? How did you come to have it?