Iirc. If you force shutdown your PC 3 or 5 times in Windows it defaults into recovery mode where your mouse and kb should work. The. You select troubleshooting and boot in safe mode.

I don’t think a Frankenphone is possible. Maybe to some extent if the screen sizes and resolution matches but I’ve seen people use old phones/screens as temperature monitors on their computers or a bathroom touchscreen news / weather screen next to a mirror

Hidguardian is a fickle beast. You probably hid your kb and mouse from device manager by accident and now windows doesn’t see them. Try booting up in safe mode and undoing hidguardian or plug in ANOTHER kb and mouse so that they get a different hwid

My cats scratched my TV and I used 100% petroleum jelly (Vaseline) to cover it up. The scratches are there but they’re hard to spot. Just take a bit on your finger, gently rub it on the scratch and polish the smalear with a microfiber cloth