Registry of Power of attorney

Our family staying at kolkata owned land/ plots at dhanbad in name of late Bhabhi, widow of eldest brother. Some locals forged a poa and hiddenly sold all land to various parties with mutation, deed and paid taxes. After knowing legal cases were fought, ads published, got judgement in favour thereby no right, claim or title by forged party. Cases are still challenged by those who bought lands on forged poa. Now to deal land matters in court cases, Is registered poa needed from legal heirs ? What is the current fast process at Kolkata registry. Charges. Thanks