Company is not providing me experience letter

Hi all, I worked for the organization from 2017 to 2020 and I resigned from the company during lock-down due to COVID-19 as company was asking us to work for more than 15 hours a day and even to work on Sunday and Saturdays. when i resigned the company they released me on the same day i have sent the resignation mail as i fight with them against there illegal rules for the employees. i got there relieving letter with the date that i am relieved from their services. but after 10 to 15 days the CEO and his so called spoon called me and tried to threat me and blame on me that i have contacted their clients outside the company and stolen their code and sell that to the my own clients. that was not true and they failed to threat me. after that they deny to provide me experience letter and their HR also block me as well.. after some days they sent me legal notice and blame on me that 1. i have leave there company without serving notice period (even they release me on the same day) 2. i have contacted their employees and stolen their code 3. i have breached there non compete and some other policies all these allegations were false and i replied with my full confidence. but there is only one question in my mind i started freelancing due to my financial condition but it was not allowed according to the company policy. even almost all people do freelancing even companies dont allow that. i want to case on the company for my experience letter. can i still case on them as i am freelancing ? but i have not used their one line of code or any client. i do my own work at night time.. please clear this to me so that i can go forward.