First of all, scalp
infections can cause hair fall
, but Dandruff
as such doesn't cause hair fall. Its the scratching and associated infections which causes hair fall.
First of all we need to examine you and see which type of hair loss you have had-as few can be reversed, few cannot. I do not know about fenugreek and onion juice and also head stands. They are out of my area of knowledge and expertise.
From my perspective, a can recommend you to consult a dermatologist
so that the doctor can decide what sort of hair loss you have, and the appropriate treatment for that. As there are a lot of causes for hair fall, and a thorough examination by a qualified dermatologist can guide you correctly.