Given that this post has been made before, and I replied to the first question, this response will address the fourth question.
Typically, people do not know that their behavior makes another unhappy (if nonverbal cues are not given--which would show the unhappiness). Unless a person is upfront and tells another person that their nonverbal cues are hurtful or unaccepted, the behavior will not change. Behaviors can only changes if a person is made aware of what they are doing. That being said, some nonverbal communications are very hard to change--many are involuntary reactions (given they have been "used" so much)--just ask my teenage daughter.