Any battery can cause a fire under the right circumstances.
If you put a battery or a cell in a fire, it could explode.
No, this will not work. Microwaving does not work to charge any battery. This can also be very dangerous. It can cause a fire or explosion. It could cause serious bodily harm and property damage. It would not be advisable to experiment with this.
yes
Yes
It would if the battery voltage was lowered enough to cause it not to fire.
It's possible. Not likely to be the battery itself it that happens, though.
Really neither.
tactile and chemical
happened on mine when the battery shorted out against the bonnet
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.
Check the charging current, it may be too much for the motorcycle battery and cause damage to the battery with risks of buckling electrode plates, cracking of the case, explosion or fire.
assuming the battery isn't just dead try yanking on the battery cables and see if you get some life. The most common cause of no power is battery cables.