All electrical devices create at least some amount of drain on your car's battery. Although the amount will vary by device, a properly wired system will charge via the car's alternator with no adverse effects.
The Legacy subwoofer will really drain your battery. It's not a good idea to run it while you're not running the engine.
Not terribly but it's best to only use while running to be sure.
A car battery in any car would drain due to a short in the electrical system.
If the ashtray light is not working it will not drain the battery.
You can get a car alarm that uses it's own battery so wont drain the car.
Could be a few things, weak alternator, bad battery, bad wiring. If you have a subwoofer in your car with no battery cap that will certainly do it.
A starter does drain a battery. The battery holds a charge so that you can use your starter to start the car. After the car is started the alternator recharges your battery and runs your car and all it's accessories. If your car won't start or is having a hard time starting you can drain your battery by repeated unsuccessful attempts to start it.
If the alternator is installed incorrectly, yes, it can drain the battery.
Yes, if the relay was stuck it would drain the battery.
leaving on the radio
No.
Yes