Hair Growth Remedies

i’ve heard that some people use Biotin to help with hair growth. i’m 19 and my hair is really thin. how effective is it? when will i start to see results? are there any side effects such as increase hair growth in other places other than the scalp? or increase of acne? also, which product is better? or is Biotin a pretty good choice? thanks!

I lost the hair on the top of my hair due to radiation and I was wondering if there are any special treatments I can do to promote the hair growth.
Should I wash my hair more or less? Right now I have some dry scalp so I use an all natural itching/dandruff shampoo that has been helping. Also, I wash my head twice a week and use a soft bristle brush to remove the dead skin and stimulate blood flow to my scalp.
Any recommendations?