Are amphetamines addictive?

Yes. And they can have serious, life-threatening side effects. They should only be used under the supervision of a doctor. If you feel you are addicted, you should get help right away.
Yes. . Yes. Why do you ask? If you have been using them, please seek professional help to stop using if you can't on your own. Do so asap.
Yes. They have a strong potential for misue but not all use is misuse.