Company refusing to give me experience letter and threatened to write derrogatory comments on it

I worked for 1.5 years at a Pvt Ltd company. When the company announced that they're shutting down their software division, I gave my 30-day notice for resigning and during discussions, I said I'll do everything in my power to wind up ongoing projects. However, this completion of tasks depended on a variety of factors like the company providing a Mac OS Laptop for releasing a mobile application to the Appstore and meetings with clients about winding up the projects, which the company has failed to conduct. The company could only provide a Macbook after 15 days post my initial resignation letter, which means 15 days of my 30 days period to complete tasks has already been laid waste. Post 30 days notice period, I stayed 7 more days to help things further, however, when it came to a situation where I had to take money out of my own pocket for travelling to meetings and stuff and my salary for previous month was not yet paid, I escalated things with management stating I need some sort of compensation for these extra days. The management tried to pin all the fault of not completing work on my head and said I need to complete all this, otherwise they won't release the salary or experience certificate. Last Sunday I was at home with family and I received some phone calls from them which I refused to pick up as it was a Sunday and usually when I used to work there they would often call on Sundays and past midnight to do work. The next morning, Monday, I received a call from the Police station saying they had received a complaint of a cheating case against me and I had to go there. When I went there I explained the case and the police officer said law is in my said and to release the salary immediately, post which I got my salary credited. Inside the police station the CEO said "in experience letter, I will write this bad experience in my way" and left the station in anger. But I have yet to receive my experience and relieving letter and I have no idea how to proceed about this. I have existing offers from other companies which I'm reluctant to follow up on due to this unavailability of experience letter. Please advice me on what I can do next. Found these articles This is a pvt ltd company in India. Kerala Shops and Establishments Act Ammendmend Bill 1960, which was amended in 2014 with new sections 5F and 5D related to employee engagement. As per this act (15)“shop” means any premises where any trade or business is carried on or where services are rendered to customers, and includes offices, store-rooms, godowns or warehouses, whether in the same premises or otherwise, used in connection with such trade or business but does not include a commercial establishment or a shop attached to a factory where the persons employed in the shop are allowed the benefits provided for workers under the Factories Act, 1948 (Central Act 63 of 1948); (4)“commercial establishment” means a commercial or industrial or trading or banking or insurance establishment, an establishment or administrative service in which the persons employed are mainly engaged in office work, hotel, restaurant, boarding or eating house, café or any other refreshment house, a theatre or any other place of public amusement or entertainment and includes such other establishment as the Government may, by notification in the Gazette, declare to be a commercial establishment for the purposes of this Act, but does not include a factory to which all or any of the provisions of the Factories Act, 1948 (Central Act 63 of 1948) apply; SECTION 5F and 5D are violated. I initially joined their organisation when it was just a proprietorship, which was a franchise of another company. Later they became independent and transitioned to a pvt ltd company and this time they never gave me any formal letter of appointment. I have a momento / trophy received just 2-3 months ago upon completing 1 year at this organization in which it is written "Happy 1 year anniversary to the mastermind at [redacted company name], your vision and commitment are the driving force behind [company name]s growth. Even just 1 month ago during a meeting the CEO personally said to another team that I have done everything for them beyond my duties and applauded me. She can't write derogatory comments on my CV just because I refused to work for free after my notice period for pending works.