02 June 2020
1. If your father is mentally retarded then better to obtain his medical certificate to that effect first and then apply to become his legal representative through Civil Court and on that basis to file a civil suit challenging all those documents wherein you smell foul play and through court, send all those documents in FSL and obtain its report and further act upon on the basis of the report.
2. The method has already been told to you.
FIR can also be got lodged directly if you file a complaint with the local police and in that event also the documents can be sent by the investigating officer to FSL.
03 June 2020
Services of the hand-writing expert can be got availed by individual also and there is no requirement of the court order for that purpose but the due reliance can be given only if the signatures are verified by FSL.