Hair oil can promote circulation and may improve the hair density and frizziness and to an extent improve the hair growth but knowing the root cause of hair fall and treating it makes the difference
Hair may not regrow totally but thinning can be managed with medical intervention but it should be treated in early stages to have better results
One of the best known vitamins for hair growth is a B-vitamin called biotin. Other hair vitamins are Vit A, C and E
Citrus fruits like orange, lemons, sweetlime. In addition strawberries, papaya, apples and guava are also good for hair.
It depends. If a follicle has closed, disappeared, scarred, or not generated a new hair in years, then a new hair wouldn't be able to grow