Yes
It's possible. Not likely to be the battery itself it that happens, though.
No
No, the battery will be overcharged and battery damage will occur if it is done.
No, a lead acid battery is a wet cell battery and a 9 volt alkaline battery is a dry cell battery.
It heats up very hot and may explode.
This is not advised! The 9-volt charger might have a current limiter so that nothing burns up, but it any case if left on it will destroy the 6 volt battery by overcharging. A 6-volt charger is not expensive.
no
A 9 volt battery is stronger than a 1.5 volt battery because it has a higher voltage. The higher voltage allows the 9 volt battery to power more demanding devices and last longer than a 1.5 volt battery.
1.3cm
a 9 volt battery
buy a battery charger
it operates a battery,mostly a 9 volt battery