Have been having intense hairfall and thinning of hair.what all tests can be performed to assess the cause behind the hairfall.no hereditery baldness?

Some ideas: If you're not a thick-bearded, super-hairy-chested guy, you won't get heavy-duty male pattern baldness in your twenties. I'm going to assume you've had your thyroid checked, and that this doesn't look clinically like alopecia areata or a brutal fungus infection. Most likely it's telogen effluvium ("shedding"), which generally self-cures. Trusting you're adequately nourished. Best wishes.