No, a fluorescent light fitting with a 4xT8 2' 18W tube and a 48W ballast does not use all the 120W when running.
No, the ballast's output is not matched to operate a fluorescent bulb.
The basic fluorescent light fixture is AC, although there are fluorescent lights powered by DC.
No. You are not.
Pull the light globe straight out of the fitting. No twisting.
Apart from no, your question has no simple answer. Fluorescent lamps need a few kV to start them and have a 90V drop when running. All of that is provided by the "gear" needed to run a fluorescent lamp. In a compact fluorescent (CFL), the gear is inside the cap.
Its good for it
Yes, if it fits the socket and the light fitting, or lamp fixture, with its cover or shade. You will not be able to dim the compact fluorescent as you did the incandescent (unless you have a really fancy dimmer).
Well.. the difference is that fluorescent light isn't natural and natural light isn't fluorescent . its not rocket science (:
If you mean the ballast in a fluorescent light fitting where the ballast is wired in series with the tube, the answer is "No". Explanation: If no tube is in place, the light fitting's circuit is "open" so there is nothing to take any current from the "hot" supply wire and return it to the "neutral" wire.
A four tube fluorescent luminaire is just 4 separate fluorescent lamp circuits in one fitting. Look up 'how things work' etc to see a fluorescent lamp circuit.
Anything that excites the gas in a fluorescent will make it light. Static electricity from the carpet will cause compact fluorescent to light.