You should always take care of your skin because it's where people base and see who you are. You should always be aware of what you're buying to avoid skin problems.
Having stretch marks means that you're losing weight. The stretched skin stays, while the fats are removed. I hope are there lotions or creams that can help you with your problem.
It's easy to grow your hair as long as you eat food rich in vitamins that supports the growth itself. You should also be aware of what you're applying on your hair.
If you're asking if permanent growth is possible without supplements. I think no, there are vitamins that are needed for our growth. If these are not present, I think there is no way we could live a healthy life.