Still have acne? If you still have acne such as blackheads and whiteheads then retin a is appropropiate. Acne does not stop at 19 in everybody. It is used only at night because it increases sensitivity to sunlight. A weaker version called Renova (tretinoin) is used for fine wrinkling in older individuals. Retin a is a relatively mild acne cream especially in the weaker strength of. 025.
Yes. I agree that healty diet composed of fresh fruits and veggies is optimal for health, but you can certainly use retin a (tretinoin) (although you may want to go with a mild potencey cream - like 0.025%). It is one way to keep your skin looking 24 years olds. Use at night and don't forget sunblock during the day.
No. At your age, I would try fresh fruits and vegetables. Retin a (tretinoin) has place for severe cases of acne.