Most likely a 220V versus 110V thing. I wouldn’t even think about trying it unless I was sure that wasn’t the case.
All computers use 12/5v power internally.... Especially laptops.
No, 115.240 comes from the external power supply that you into the wall. The regulated internal power comes off the power rail on the MoBo.
An inverter is a stepping and converting device. It converts DC to AC using it’s own on board oscillator. It increases (steps) and then decreases the voltage, as needed, to cause the gas in the bulb to radiate, or “ignite”, and glow at a controlled rate.