Some esoteric hackery. I read about blue-boxing, but never even saw the hardware required. You should write a book about this stuff. Nearest I came was picking up an issue of 2600 in the States.
My dad had a Cavalier SRi. I think his was silver. Not seen one in a long time.
There was none, 'The Little Operator' was software and ran on the PC. You needed to be 'trained' to use it. I fell short of paid lessons!
I looked mine up a few days ago on the DVLC site. I remember the plate number. It's currently not taxed, being a 'D' reg that's not surprising.
Amazingly I remembered the registration of my dad's. It's not been taxed since 96. You would think they would record if it was scrapped. I just sold my Hyundai for scrap as it was not worth fixing. Had a good 10 years out of it. Now got a Peugeot that's actually older, but has less miles and is actually quite nice.