No, you must use a 14.4 volt charger.
No, you can not charge a 3V battery with 12V charger.
No
No
No.
can a 12v lawn mower sealed battery be charged with 12v battery charger use on cars
NO, voltage of the charger must match the battery voltage.
Depends on the amperage of the charger. A 10 amp charger will charge it in about 1 hour.
yes
No, you need a 24 volt charger.
Yes, the amp hour rating gives you an idea of the capacity of the battery and charger. The charger and battery need to have the same voltages. i.e. dont try to charge a 6v battery with a 12 v charger. The battery will be charged until it is full.
You can but you can alos easily overcharge the battery.
Yes you can. The charger has what is called a trickle charge and will need to be left charging at least overnight and maybe for two nights dependant on how little charge the battery has left.