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.
Yes. For example, meth-amphetamines. They are addictive.