How to unlock iPhone 12

Which One?

If you forgot the passcode on your iPhone, or your iPhone is disabled or unavailable -

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

If your phone is carrier locked - How to unlock your iPhone for use with a different carrier - Apple Support

How to unlock your iPhone for use with a different carrier - Apple Support

If your phone is Activation Locked - How to remove Activation Lock -

How to remove Activation Lock - Apple Support

Is the whole display screen turns RED??

provide some additional information so we can understand more about the issue