Stereo install experts

[WESTY66]

I’m starting to wish I’d never started this!! I should have left the single din radio in??

 

[aba]

The white plug could be for steering wheel controls if fitted or an auxiliary input to the factory stereo

 

[WESTY66]

Right, home from work now and I have some daylight!! Everything starting to make sense except the reverse feed!! I’ve tried to get rear lights off but they’re not budging and I don’t want to force them in case I break some tabs off or summat like that!!
I’ve got the gator off the gear knob and there’s some wires underneath SURELY One of them will send a reverse signal to the stereo??? Yes?? No???