0.5kg of gas.. because the whole 0.5kg of kerosene is already burnt out.

You put it in the lamp. You find the lamp by going to the fireplace and playing the clock game. The lamp will appear, then go to the basement and click on the kerosene barrel. ;^)

1898

Same way a regular kerosene lamp is made. It's mainly the casing and the bracket that's different.

The time autonomy of a kerosene lamp is all dependant on the type and age of the lamp. Another big factor in the time autonomy is the size of the lamp as large lamps will either need more fuel or will not last as long.