Employer refusing to give the experience letter after providing the documents as reason to quit

Hello, I have been working with this organization form past 1 year I have faced many issues in this organization but this one was extreme. I have to shift to my hometown for family emergency I did provide the document showing the emergency is unavoidable. Company is still refusing to provide me the experience letter, I did not even asked for the salary for the days I have worked. I sent an official email to the supervisors and the HR requesting to accept the resignation and they refused. There are things which I feel are unlawful. 1. Company does not provide Paid (No sick leaves, no casual leaves or maternity leaves) leaves whatsoever. They claim that there is a leave en-cashment at the end of the year only if employee completes 18 months in the company. That amount cannot be considered as leave en-cashment as from that amount employee gets the deduction and nobody knows what are those calculations 2. There is no PF, Insurance or any other government mandatory facilities. 3. Employees are getting terminated now and then without prior intimations/ warning letters. 4. This company is working for an American Company based out of Pune Maharashtra however there are no National/Government holidays for the employee or a Double pay (Kamgar Divas, 15 august, 26 January, Diwali etc.) If you want to take a leave the salary will be deducted and if that particular holiday comes in on Friday or Monday your Saturday and Sundays salary will also be deducted. So you are loosing 3 days salary in a row which will not be even counted in the leave en cashment policy. 5. No security for females, No night allowance, No Salary breakdowns in the offer letter. 6. Company does not have it's own PAN and TAN Number so the company is not paying it's taxes. Company deducts 300 Rs every month from each employee's salary in the name of professional tax but I am sure it does not go for any tax payments. 7. There are not more than 10 employees in one branch, they keep switching these employees on different payrolls so that government would never come to know that this is almost a scam. I want to take a legal action on this company but I don't know how I should proceed. I want my experience letter as it will affect my future as I have never absconded from any Organization before.