If I were troubleshooting the vehicle I'd use starting fluid to see if the engine will fire briefly.
If the engine will start using starting fluid but dies immediately when you stop using the starting fluid I'd suspect the fuel pump gave out after running "dry" for an extended period of time.
But don't just replace parts until you've tested them. If you suspect the fuel pump make sure you verify before throwing new parts at a problem. ADDED: Good advice. I "like" the fuel pump possibility best, especially on a vehicle that old. Another possibility however; since the gas tank was sucked dry, it is possible that the fuel filter became clogged with the crud that normally gathers at the bottom of the gas tank but doesn't usually get sucked into the fuel system.
Because the alternator keeps the battery charged when the car is running.
Yes
No , for the battery to be charged the engine must be running . This means that your alternator , if it's functioning properly , is charging the car's battery as the engine is on/running .
If your engine is running , and the battery light comes on , that indicates that your battery is not being charged
You should read 12.6 volts with a digital volt meter on a fully charged battery with the engine not running.
You cannot charge a battery without a battery charger or having it charged by the alternator in your vehicle while it is running.
That it needs to be charged or is running out of battery.
If the engine is running, then no. The alternator constantly keeps the battery charged.
Typically 14 to 14.5 volts assuming a fully ( or nearly) charged battery.
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 battery is kept charged by a generator or magneto when the engine is running. It is located under the flywheel.
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.