Agricultural land not converted in to Residential Purpose, But building constructed

My brother-in-law wanted to buy a property in Marathahalli, Bangalore. He found a property which has two buildings constructed in the same land and decided to buy both buildings to make Single building in future. He bought one building and registration done at sub-registrar office. We knew it is an agricultural land of 3 Acres, and owner divided that land into several partitions and sold those partitions. Many have bought those properties and constructed buildings on their land. These two buildings are also constructed on those divided partitions. Actually there is court case on owner properties filed by owner family members. Owner is telling that court has given decision in favour of him providing a certificate/some document in the local court. Now we have applied property loan for Second building. Bank asked us to provide several documents which owner has to give us. we have asked below some documents from owner.. 1) Land conversion certificate from agricultural to residential. 2) Original Mother Deed & Gift Deed. 3) Tax payment receipts. 4) EC which he is holding. 5) And some other documents includes Land layout. 6) Some documents bank field officer arranged for us. Now we got to know that this land is not converted from Agricultural to residential. he doesn't have that certificate. Bank process everything is done and only Lawyer legal opinion is pending. When we asked for Originals, owner is saying he can't give us the originals since the documents are for 3 acres. And he said that he will arrange us the latest certified copies from Sub-registrar office and he did. But banks lawyer is not accepting these certified copies. he needs only originals. But owner told that court Lawyer has the documents, So we had to wait for some days. We waited 3 months, but didn't get originals and bank loan is also expired. We have paid some amount to the owner for second building and thought remaining balance will be given through loan. Now owner told us that he would return total amount for the second building that we given. We have applied for B-Katha certificate for building we bought and got B-Katha after we payed the balance taxes which owner has to pay. After some days BBMP person calling(Shouting like anything) us to clear the old balance for building we bought. We told him that we have paid latest taxes and got B-Katha. But BBMP said, Owner didn't pay taxes for the buildings that he has constructed from starting. Only he is paying taxes for Land only. we have already sent many notices to owner. You bought the building now so you have to pay." We expected that owner bribed this BBMP person and this same BBMP person expecting some amount from us. We understood that owner playing game with us saying that we have paid less tax and insisting us to clear that balance taxes. Please give your valuable points on this - After 2nd building registration also done, we planned to apply Land conversion certificate - what consequences we face.