More details are needed.
I presume this is a vehicle. What sounds does it make, does it start to turn over?
The problems could be damp or other earthing problems, fuel pump problems, starter motor, etc.
If you need to jump start the car then the battery may be fully charged but it is defective and needs replacing. A full charged battery will read 12.6 volts at the posts with the engine not running. 12 volts indicates the battery is only 25% charged.
As long as the battery is fully charged it will start no matter the condition of the alternator. Eventually the battery will run down if the alternator is not keeping it charged.
As long as the battery is charged
if the battery is good and charged sure
Yes.
Yes they could be cleaned and battery charged
Low/bad battery, bad battery connection. If the battery isn't getting fully charged you might not be able to start. If it isn't getting charged, check the alternator.
It will start if there is enough charge in the battery to turn the engine over. However if the alternator is weak then the battery will not be charged fully.
Is starter working?
When using battery cables to start a car, once it has started is there a procedure when removing the cables from the running car?
the alternator is bad
You can get a new battery, you can jump start the car with jumper cables and another car with a charged battery. You can also put a battery charger on your battery to give it a charge.