A black hole forms when a high-mass star dies. It basically emits no radiation (light) hence the name black hole. It's gravitational field is so strong that matter in its vicinity gets pulled in and lost forever. Nothing can escape its gravitational pull - not even light.
I'm sorry I just skimmed through your post and didn't even read the last question. Since speed of light is the fastest speed allowed in physics, which means nothing can exceed the speed of light. There is a concept called escape speed, which is the speed needed for one object to escape from the gravitational pull of another object. An object's escape speed is proportional to the square of the body's mass divided by the square root of its radius. So the more compressed an object is, the more escape speed is needed to escape that object's gravitational pull. Now a black hole is basically the core of a high-mass star that collapsed on itself and is compressed down to a point where even the required escape speed exceeds the speed of light. But remember, nothing can exceed the speed of light since it is the fastest allowed speed in physics. Therefore, the conclusion is nothing can escape from that compressed object, or in other words, a black hole.