Regarding Cheques issued 20 years back- against Loan availed

Hi, Greetings, I am Natarajan from Chennai and have availed loan of Rs 2 Lakhs from an agent of private Financiers during 1996-1998, when I was running bad patch of financial difficulties. Against the loan , I have issued 25 Blank Cheques , 4 Promissory notes ( Blank) and the financier was supposed to return the cheque after making payment. But, unfortunately, though I have repaid as Cash on several installments and fully settled the liability during 1998 , he has not returned Cheques and promissory notes and promised to collect from all the financiers, who have lent the money and return. But , he has not fulfilled his promise,. At the same time , he has deposited cheques and got it returned, Meanwhile, I was hospitalized for heart operation and in this melee, I have forgotten to ask the documents., After settling all my dues, I have also closed my accounts in the bank. Now, after 20 years, he has contacted me last week and demanded Rs 18 Lakhs towards principal and interest for 20 years. I have no papers to prove my payment since the transaction took place before 20 years.. But , he says that he has returned Cheques and promissory notes. Now, can he file a case against me under Cheque bounce case? I presume that case to be filed within stipulated period from the date of cheque bounced. Can he put the latest date in the promissory note and file the case, When I ask him why he was keeping quiet for the past 20 years, he said he could not locate me. When it is not possible for him to locate me for 20 years, how can he put the latest date in the promissory note. If at all , he has to put the date 20 years back only, which case, I feel that promissory note may not be valid document. Now, stroke of my signature is changed in the year 2000 itself and in all Govt documents like Passport, Adhar, IT etc, bear the changed signature only. I shall be thankful if you will kindly advice me , how to handle the situation, Thanks & Regards Natarajan Chennai 09940637494 / 09791005726