The same way you charge any battery, by hooking it up to an appropriate charger.
You will need a charger with 24 volt capability.
no it can't
Yes
Not all solar panels can directly charge a 24-volt battery. To charge a 24-volt battery effectively, the solar panel's voltage output must be compatible, typically requiring a panel or a combination of panels that can produce at least 24 volts under load. Additionally, a charge controller is recommended to regulate the voltage and current from the solar panel to safely charge the battery and prevent overcharging.
Not by connecting them directly, that'd be too powerful.
Separate the 2 12 volt batteries and charge them individually.
No, you need a 24 volt charger.
I can if I charge 2 of them at a time. Most 24 volt chargers also have a 12 volt setting. What is hard to find is a 32 volt charger. We can charge a 12V battery with 24V charger, by connecting two 12V batteries in series i. e. the negative terminal of the first battery is connected to the positive terminal of the second, now the charger positive terminal is connected to the first battery positive terminal and the negative terminal of the charger is connected to the negative terminal of the second battery.
You would need a 24 volt charger. Connect them in parallel and you can charge them both with a 12 volt charger. Or disconnect them and charge each one separately.
Most 24 volt systems use 2 or 4 12 volt batteries. Be careful not to let the cables get mixed up. They need to be put back in the same spot. Disconnect the battery, Charge each battery individually, Reconnect the cables exactly like they were before. You are ready for work.
Yes, a 12 volt battery will be damaged if charged with a 24 volt charger.
Yes, only it will take the 1.2 amp a little longer to fully charge a battery than a 1.5 amp charger.