Scenario A is impossible and has been impossible for as long as https has been a thing. The only way it would be possible is if you installed a root cert from

Scenario A is impossible and has been impossible for as long as https has been a thing. The only way it would be possible is if you installed a root cert from your ISP onto your computer so that it would trust a cert issued by them. Otherwise, they would not have a valid cert for example.com and you would be presented with a cert error. This is literally the exact thing https was designed to prevent. It is and always has been impossible (again, unless the client machine is administered by the ISP or whoever the middleman is, and they can install a cert on the machine)