This is illegal.
It is good that you have the evidence of having worked.
Is it sufficient to prove that you were asked in writing/on record to work like it?
Have you recorded the threats of the Manager.
>>> When you initiate a query on such matters post following information in 1st post itself, pointwise!
What is this establishment registered as: Commercial,Industrial?
What is its line of business:IT,ITeS,banking etc?
How many maximum persons are employed in it at any point of time, before and after your resignations?
Is the person designated as HR Manager has been authorized to sign acceptance/declinature of resignation, by Board resolution? Is he/she your appointing authority or MD?
Did you record the discussion/threats (audio/visual/minuted/witnessed) of Manager? Do you have any evidence of it?
The Redg Office, Corporate Office of the company, and your reporting office was located in which state?
What was your designation and nature of duties?
How many persons were reporting to you?
Did you have power to sanction leave/increment/appoint/terminate?
You have worked for how many months?
Do you have leave policy, HR policy, Service Rules and Regulations, Conduct and Discipline Rules, Exit Policy that are mentioned in the appointment letter?
Is it stated in appointment letter that notice pay in lieu of notice period can be tendered?
What was your monthly salary?
Was any appointment letter, salary slip of each month, PF number with a/c slips, ESIC card,Form16, given to you?
Did you mention NO tasks are pending at your end and to whom you should handover the charge?
Are you a member of any employee’s/Trade Unions?
Have you consulted a lawyer and what is your lawyer's opinion?