Hi
In any sale deed, the seller is bound to indemnify the buyer against any losses arising as a result of disputes in title of the property.
Since the property is registered in your name and also that the patta passbook is issued in your name, you can file a cheating case against the seller and also file a suit for declaratory title in the court and get the land of 2 acres regularised in your name by making the seller pay the land regularisation charges.
The merits in your case is that
a) Registration of property has been done( If the land was assigned lands, then the registrar should not have permitted registration of the property in the first place as assigned lands are in prohibited register).
b) Patta passbook are issued to you.
Also andhra pradesh government has permitted regularisation of assigned land transactions with effect from 2016 and buyers can regularise the transaction by paying the regularisation fee.
So, the suggestion is penalise the seller by filing a criminal case and also a civil suit for declaratoty title and make him pay the regularisation fees from regularising the land from his pocket.
Hope this information is useful