ECU 's made by man or locked by a programme -can be unlocked by another man, just ask Elon.
Quite possibly, but what you may find is an error message is created once the software has been accessed and picked up when the car is next scanned for servicing or annual road worthy testing or if any accessory of the car is connected to the internet etc. It becoming increasingly important that core software cannot be hacked as we move to cars self driving etc.
