It would be impractical to try to write everything here, so here are a few pointers. (I used to play rhythm, lead and bass when I had a rock band. But I've had no time for it for years and my fingers are stiff and I've largely lost the touch. But the basics are still the same).
I strongly suggest you learn playing rhythm on an acoustic guitar first before concentrating on lead. Without acquiring a good feel for rhythm, you'll never make a good lead or bass guitarist.
You didn't say if you're a raw beginner or one with some basic skills. Assuming the first, get some guide books on the basics. Learn the major keys, then minors and gradually proceed to more advanced stuff. At the same time, try to strum along to recorded music with good beats. Pay close attention to keeping accurate timing. Learn different beats.
Playing bass guitar is not as simple or unimportant as you may think. Sure, you can get away with monotonous plunk-plunk-plunk to some extent. But a good bassist syncing with the drummer can really set the mood of a song.
Start learning lead after you've got a good grasp of rhythm, not before - that's a mistake many aspiring guitarists make.
On to some of your specific questions:
Plucking is where you strike the strings singly in succession using all the fingers. It's somewhat like lead solos, but in plucking, you generally keep a basic flow in timing without pulling on a string to get tonal variations.
A pick-up is somewhat like a microphone (mike) for a guitar. The difference is this: A mike generates tiny electrical voltages when air vibrations (sound) strike a diaphragm. In a guitar pickup, a coil of wire is wound over a powerful magnet and the magnet-coil assembly is mounted close to the guitar strings. When the string vibrates, it disturbs the steady magnetic field and this generates a voltage proprtional to the string vibrations.
Time? It depends on how diligently you practice, and on your environment. I live in a social environment where western music is widely practiced and every child grows up with it. I guess this makes a difference. A large percentage of the male population (and many females) can play a guitar passably. If you practice regularly and listen to records carefully, you can pick up some basic skills in a few months. This is when you learn on your own. If you can take some tuition, it will take less time. To become really good, it takes at least a few years. Most of all, pay attention to timing and rhythm.
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