Login to i.mi.com and unlock your device, then remove your device from Find my Phone. Even then it might take many tries for it to accept the login on the phone.
The SIM settings on my RN3 running 12.1 are greyed out, it's still working fine, can send & receive calls & texts, but can't change my settings.
Edit: I'd frozen the "SIM Activation" app, unfroze, rebooted and ok again. Oops.
This is based on the beta build. Beta software should not be relied on to be stable, that's why it's beta. This version is based on Xiaomi's dev build, not the other way around.
I suspect Android Auto is just a very poorly designed application. I use CarHome Ultra which has a lot more functionality and that works just fine, although it might not look as pretty. AA takes several seconds to open up any of the sub-applications (Maps\Music) when told to.
So have you tried it and it doesn't work on whatever model your particular phone/ROM is?
Works fine on my RN3 with 6.12.1 as a standalone app although it's painful to use as it's a massive CPU hog and the RN3 struggles.
Tap on the USB notification on the phone and change it to file transfer mode if you haven't already.
Otherwise;
Try Mi Suite; http://pcsuite.mi.com/
Or the tutorial here; http://forum.xda-developers.com/elephone-m2/help/windows-10-mtk-vcom-usb-drivers-32-64-t3267033