Sections 138 1nd 139 ni act

My friend ‘A’ sold an immovable property for Rs.20 lakhs. An individual ‘B’ known to ‘A’ was accompanying the purchaser all the time. After the deal was completed, when B saw A was getting so much money, he asked him to pay Rs.1.0 lakh as brokerage. There was no understanding between A and B for any brokerage. Further A felt that a brokerage of Rs.1.0 lakh was too high for Rs.20 lakhs. But B was a thug of the locality and so intimidated A and got a cheque for Rs.1.0 lakh. On the next day A gave ‘stop payment’ instruction to his bank. So the cheque bounced. In due course B sent lawyer notice to A to pay the amount. But the reason given for the payment was not the actual one. The notice stated that 2 years back A had taken a cash loan of Rs.1.0 lakh from B, When B asked for return of the loan A dillydallied for returning the loan and finally gave him the cheque for Rs.1.0 lakh. It is not clear why B did not mention the real reason for the cheque. Anyway it was utter falsehood that B had given a loan to A. There is no written document. B had only mentioned the names of alleged witnesses, which was also falsehood. The intention of B to give such false reason is not known. 1. If B goes to court, will he have to give the same reason as stated in the lawyer notice? 2. If A successfully rebuts the loan story, will he have to give to the court the real reason for giving the cheque? 3. If he gives the real reason and the court feels that he was liable to pay the amount to B for that reason, will A have any civil or criminal liability under Sections 138 or 139 as B himself had not claimed the amount on that account?