Seller of any property will have to submit a detailed Valuation Report of fair market value as on 01st April, 2001 (if the property is acquired before 2001) accompanied by the Income Tax Returns (ITR) to substantiate the calculation of Long Term Capital Gains Tax (LTCG) on the sale of property. If an immovable property has been sold on / after 01st April 2017 then it is probably required to submit Valuation Report from a Govt. Regd. Valuer detailing the Fair Market Value (FMV) of the property As On 01st April, 2001 for calculating Long term Capital Gain on the sale of property
2) it is not necessary that it should bear sign of sub registrar
3) your CA can guide you as to costs for obtaining certificate