Found a button
#5
Thats not a stock button. Follow the wires and see where they go.
#8
They're bringing the Holden VE Commodore (AKA Pontiac G8) back as a cop car. We're all screwed!
#9
Could have been for anything... Fog lights, ECU programming, e-brake bypass for an in-dash DVD player, water-injection to cool the turbo. Whoever had the car probably removed whatever it was there to control when they decided to sell the car but left the button just so as not to leave a hole in your underdash.