nope. you might have to clean the terminals to the battery with a wire brush, but it doesn't hurt the car at all.
It will probably keep transmitting and place a small drain on the battery.
leaving on the radio
The car light? YES! Leaving your car light on WILL make your battery run out. Things like leaving your car door open if the light is on because it is open will cause the lgiht to Mae your car battery run out. There is a big difference between shorted out a car battery and running the battery down. Lighting in itself won't short a battery out but will run it down.
mainly leaving your lights on when the engine is of or leaving the keys in the ignition
no
If the engine is running, then no. The alternator constantly keeps the battery charged.
many things can do it suck as junk battery, junk alternator , or leaving anything on in the car
No, not unless the ignition is turned on.
Eventually, yes, it will.
if you boost charge a battery you should discinnect it from the car. if not you may burn out the alternator
Yes, bu very slowly. Will cause dead battery in about 1 month
Leaving the car stereo on overnight can drain the battery and make the car impossible to start in the morning.