3 hours
If it is an automatic charger let it charge until the charger shuts off.
As long as it is a 12 volt battery you can if you set the charger on low.
14 hours approx
A trickle charger is a car battery charger that is designed to be left on a car for very long periods of time to re-charge that car battery by slowly adding charge to the battery.
You do not charge a 7.2 volt battery with a 9.6 volt charger period unless you want to ruin the battery. You charge it with a 7.2 volt charger.
I doubt the charger is putting out 30 Amps on a slow charge. need more info on battery and charger.
With a charger specifically designed to charge this battery.
As long as both batteries are the same voltage, you can jump start with the battery. If you want to charge the battery then use a battery charger.
A .6 amp charger is a trickle charger. It would take days to charge a dead 12 volt battery with this charger. You need a 10 amp charger which will charge it in a couple of hours.
Depends on the amperage of the charger. A 10 amp charger will charge it in about 1 hour.
Depends on how low of charge the battery is. I would guess around 6 hours on a dead battery. I suggest you use an automatic charger so you do not have to guess.
A very, very, long time with direct sunlight. Charge your battery with a battery charger