Property dispute, plot sold twice

Issue legal notice to seller and other vendee, followed by a suit for declaration and permanent injunction.

Besides this file a police / court complaint against the vendor.

If you are in possession since 2015, never part with possession and file a complaint to the police for cheating against the seller.  Your sale deed if registered is legal and it is presumed that your father has mutated the property in his name, the tax paid receipts are in his name.  The sale deed of the other is invalid.  Please consult a local advocate for the remedy possible as there is no harm for your possession and enjoyment with mutation and tax-paid receipts since 2015, and your father is having a legally valid title deed.

As you are in possession, you may move against the seller of executing the deed.  It is advisable if, in the first instance, a legal notice is issued to the seller.

Since you have the registered title deed on your name as well as the property is in your possession, you may file a suit for declaration of title to your name as well as for mandatory injunction restraining the other buyer from interfering in your possession and enjoyment of the property.

Police is not helping us to file FIR against the seller even after many complaints. Seller has filed a case in civil court related to RCS-A Under Act Specific Relief Act 1963 Section 34 to cancel the registry of other person but this case was filed in February 2021 and no hearing has happened so far in this case and next date has been provided for November 2021. Due to this issue we can neither sell nor construct on our plot. As per my understanding seller is trying to stretch this civil court case for long in order to avoid payment of registry cancellation fee (stamp duty) of other person. Please help how can we get either complete ownership of plot or cost of plot as per today's circle rate ?