ABSOLUTELY! One day will suck the amperage out of the battery. Hook a battery charger up @ 2 amps to charge a dead battery. A slow low charge is better when the battery is dead.

After 4 days, of course the battery was dead.

Yes that is normal for your battery to be dead

Yes when your car is not running and you leave a light on or anything using electricity it will use your battery, you should be able to jump it, but the battery may be old and not able to hold a charge.

Yes, as when the car is on the alternator is replacing the charge back into your battery. If car is off then it will drain.

No it is not normal to leave a light on for four days; it will drain the battery.

Yes.

Very normal!!!! Mine dies after a day

Yep!