In my opinion, a dream is something you imagine, maybe a dream of becoming the world's best singer, or simply dreaming you got an A on a test. Let me answer your question with a question, do you know one person that has never dreamed that the result was different than what is was?
Yes everyone has dreams except sometimes people don't remember but everyone always has dreams.
Yes, everyone has dreams. If humans didn't dream they'd go crazy as it's the brains way of releasing stress. Most humans that sleep properly (no insomnia) go into a REM sleep (deep sleep where the eyes constantly go from side to side with lids closed.) Humans dream every 1/2 hour, but usually don't remember any of the dreams. Dreams they do remember or nightmares are generally the first few seconds before you wake even though the dream may feel like it's gone on forever. Scientists that study dream patterns in people believe that a person will awake before any harm comes to them or they would die. eg: Dreaming you are falling off a building and flying through the air. You'll wake before you hit the ground.
No, studies have shown that damage to parts of the brain (often the parietal lobe) can stop dreaming completely. Though it is safe to say most if not all people with normal brains do dream, though not all of them remember it.