you should always buy flat which falls within jurisdiction of municipal corporation
2) in such a case you would have OC issued by PMC and you can be satisfied that flat has been completed a per sanctioned plans
3) ask builder to obtain completion certificate from panchayat that building has been completed as per the plans approved by panchayat
4) we are not aware whether for gram panchayat land OC is required or not . local lawyer can guide you in this regard