St/sc land to be registered in general candidate name with possesion of 15 yrs

The subject land has been allotted to SC person, who cannot sell it. You were required to verify the fact from concerned authorities on the subject.

Recheck terms and conditions of allotment.

If it is an assigned land, the land to whom it was allotted shall obtain permission from the District Collector to transfer the land in any manner.

check the local land laws for-

if there are any precondition for alienation of granted lands by the govenment ?

is there any non alienation period in the granted land ?

Are the conditions are complied with such precondtions in previous transfer?

Has he(SC beneficiary) obtained prior permission from government to sale the granted land. if not the transfer is null and void abinitio.

The assigned land cannot be sold before expiration of the conditions to alienate or sell.

Since you have not purchased it by registered sale deed, you can cancel the agreement and demand return of your amount

But sir at my location some advocates are saying that this can be done after going through application of " Dhara 80"

I think Dhara 80 is not relevant to your query.

"Dhara 80" of which Act / Law ?