It's possible. Not likely to be the battery itself it that happens, though.
Yes
No. The battery will be charged at a rate which is 2* the normal rate. This will cause the battery to overheat which might cause it to explode.
Any kind of spark can cause a fire in the presence of an accelerator like gas fumes. It can happen even with a 1.5 volt battery.
fresh battery will be about 14000 volt to 20000 volt but very little amp
Absolutely not! It is a 14 volt drill. Use a 16 or 18 volt battery will destroy the drill in short order. It will run but not for long.
No
if it is any think over 1 volt it is not a cell battery it is just a 6 volt battery if you had a 1 volt then it would be a cell battery
No, it will overcharge the 6 volt battery.
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.
The battery is a 12 volt.
No
no, there is a high probability that it will explode