Right lets all take a breather...
On the other side of the pond, older cars, well yank tanks, are bit different. You can interchange parts from manufacturers, wiring is more basic, something like a Range Rover is a bit of an odd beast with parts than can be unique to the specific model, year, variant or vin number.. most in North America have been converted to coils rather than the back art of EAS, which many if us find quite simple for example. thoigh we also have coil sprung ones here too. but thats yet another thread.
He fell in love with something with a green oval that is complex and unusual and its bitten him hard. partly from trying to undo unknown electrical work.
Yes he screwed up by treating it like a Bronco, Renegade or a Suburban.
We are after all a community, we've all had issues from time to time. the OP is on steep learning curve. we'd do better to pitch in help, and show that Range Rovers are not bad as considered and the community is, well, a community, not a galdiator arena.
OP. you need to be clear, as i said before of exactly what you have done, the sequence, and what you have uncovered. had we known about the aftermarket remote start and wiring of it to the audio you probably wouldn't be advised to go off on a wild goose chase maybe tgus coud have been fixed by now and tou could be running.
There is a lot of expert knowledge on here front to back top to bottom on the RR.
As you have discovered these are complex and not yank tank engineering. The learning curve is steep and fast.
Have you downloaded RAVE yet ? You need to do that and look at the wiring diagrams.
We're here to help
@Saint.V8 knows more about these than most will ever.
@martyuk is an electrical yoda on these.
Hang in there, follow the advice, we'll get you running but you need to be explicit in information.
There is no lack of pride in not knowing, or screwing up. I've done it, you've done it we all have. yes, audio installs are your job, but not on these. that is a whole other world of hurt with DSP, door amps, boot amps, subs, odd driver sizes, and ohm differences. if you follow the advice here. You'll end up being a guru on green ovals for your region.