A twelve volt charger will charge twelve volt batteries only unless it has a feature that allows you to change the chargers voltage. But on fast or slow charge 12 volts is 12 volts so most 12 volt chargers are only good for 12 volt batteries.
Charge it with a 12 volt battery charger.
No, a 12 volt charger will overcharge a 8 volt battery and destroy it.
A 12 volt battery charger is designed to charge 12 volt batteries.The answer to the Related Question explains how any battery charger works.
If you are asking the question, can you charge a 6 volt battery with a 12 volt charger, the answer is no.
No, the battery charger has to match the voltage of the battery it is to charge.
No.
no it can't
No it will not work
No
NoNo
No you cannot.
No, an automobile battery charger outputs 12 Volts. This is far too many volts to charge a 5 Volt battery. You would destroy the 5 Volt battery with this charger.