1) at the outset it may be clarified that without going through the documents cited by you in your query no clear opinion can be given .

2)if your leasehold property was mortgaged to bank no third party rights could be created by the owner without prior approval of bank . verbal information is not sufficient . you need NOC in writing from bank .

3)you could not part with possession of leasehold property to proposed buyer . your sales agreement with buyer is invalid .

4) let the bank take steps to declare your agreement with buyer void . since public money is involved and property is mortgaged to bank DRT would be inclined to garnt bank necessary reliefs .

5) as far as specific performance suit is concerned mention that since property was mortgaged to bank and bank has refused to give consent property could not have been sold to buyer . offer to refund money with interest to buyer

bank is only concerned with recovery of its money . if its dues are recovered it wont be interested in any legal battle .

try to arrive at an amicable settlement with buyer . if not possible then dont repay the bank . let bank take recovery proceedings .

if settlement is arrived at with bank then bank would have no objection to sale of property to the buyer

bank is only concerned with recovery of its money if dues are recovered will not be interested in any legal action

thanks for your appreciation . bank wont raise any objections for sale of the property to the buyer . obviously buyer will before making payment insist that bank give its consent as it s dues are being paid

my pleasure