How Does Android Auto Work?/Related Stuff

[gudenau]

I'm quite curious how Android auto functions. What I know right now from observations and experimentation:
- It's a video stream (compression artifacts)
- My car is a USB host, putting the phone in device mode
- Applications are on the phone
- Minus the stuff that works without the phone
- It overrides bluetooth settings and force pairs

I want to know a few specific things:
- How does the car negotiate with the phone?
- How does the video stream work?
- Can I stop force pairing?
- Can I modify the video stream?
- Can I somehow force the car into device mode?
- Can I get access to ADB on the car without GM's blessing?

Any other general technical information would be nice too, this stuff is impossible to search for.