What I can read from his post that he brought another battery, (not car?) and hooked it with his car's battery and tried to start and the trouble started.
Isn't different than jump start from another car whose engine is start and it's alternator is also providing power/current to the donor battery.
He has also not answered the question if he attached the leads on correct terminals. A wrong connection may have blown some fuses if not any other electronics including ECU.
I asked him to change key FOB battery and check. Let's see.