Why can you start a car with a battery outside of the car?
Sure, connect it to the car with jumper cables.
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.
Yes, A car battery can have enough charge to turn on car electrical components but not start the car. This is not much of an indication of a bad battery however. Use a volt meter to test the power in the battery. If the battery seems low put it on a trickle charge. Most modern chargers will tell you if your battery is bad or not. The battery also has to be load tested to…
If your battery is dead then you are going nowhere therefore why would you need to take the car out of park? Get a jump start from another car with a good battery and then you can start your car and drive to the nearest battery dealer and buy a new battery if need be. Otherwise just put a battery charger on your battery and let it fully charge.
Do you mean "jump start"? If so, yes- it requires a car with a good battery, and a set of jumper cables- connected the RIGHT way between the two vehicles. With older vehicle, it was possible to "push start" the car with the dead battery- but with modern electronics, and a completely dead battery, will not work.