Answer to Question 1
The primacy effect states that the initial impression we make when meeting someone new has a greater impact on his or her perception of us than later information. Whether people intend to or not, they make judgments about people based on their first impressions. Since first impressions stick with people longer than later impressions, a positive first impression in an interview situation means that you are more likely to be judged favorably by a potential employer.
Answer to Question 2
Arrogant people think they are perfect or know everything. Self-confident people understand themselves and their abilities.