Can I take legal action, against pervious employer

Hi, I have multiple question and doubt with my pervious employer, PLEASE HELP me. I started working for a proprietorship firm (e.g ABC XYZ) in Oct 2006, without any offer letter (because it was my first job and I had no idea on this). I was getting salary from ABC XYZ in my HDFC salary account. In Dec 2014, He started another proprietorship firm (e.g AX Infotech with pervious logo) and migrated our salary account from HDFC Bank to ING Vysa Bank. He didn't asked us to resign from pervious proprietorship firm and join another company. There was no written intimation on name change from my pervious employer. I started receiving salary in ING Vysa Bank and I closed my pervious salary account in HDFC bank. In May 2015, He converted or started another firm AX Infotech LLP (I am not sure on this, if he started or converted pervious name with same logo). Again, there was no written intimation from my pervious employer on above name change. We started receiving salary in same ING Vysa bank account. In Oct 2020, I resigned from my post with written one month notice period and I asked my pervious employer to relive me with reliving letter and experience certificate of 14 years. On last day of my notice period, he provided me 2 different letters, one from AX Infotech(back dated) and another from AX Infotech LLP(current date), in which he mentioned. XYZ employee was working with us from 1st April 2015 till 31st March 2018 and he has been relived from responsibility with all his dues cleared. (Letter date 31st March 2018) and second letter was like, XYZ employee was working with us from April 2018 till 6th Oct 2020 and he has been relived from his responsibility with all his dues cleared (Letter date 6th Oct, 2020). After checking those two letters, I asked my pervious employer to provide full experience letter. But he was hesitating to provide my 14 years of experience letter and said me, he will consult with his CA and he will let me know. I know, he is trying to steal my gratuity amount of 14 years. I got my new job on my experience, which is 14 years. My current employer asked me to submit declared experience letter in next few weeks. I am confused on above scenario and need help. I don't have any payslip of ABC XYZ, because he never provided official. I have last 4 years Form 16A (e.g 2016-17, 2017-18, 2018-19 and 2019-20) with me. I also have call recording, when he gave me warning to destroy my career, just because I resigned from my post. Please help me to let me know, can I take any legal action against him for experience certificate and gratuity.