You may go thru Shops and Commercial Establishments Act of your state which should be available at the website of Dept. of Labor Tamilnadu or you can download from internet or buy from market, and go thru clauses on Notice of dismissal, Hours of work etc..
Record the meetings (audio/visual) and keep evidence/witness with you when you are being forced to write your own resignation or face termination.
Since you are being coerced and forced to resign you can raise Industrial Dispute now. Approach Inspector under Shops and Commercial Establishments Act, labor Inspector, ALC in o/o Labor Commissioner.
You can approach Trade Unions also. The trade union leaders can be your witness. Meet them in person as ap.
If you have been working for more than 8 hours/day lodge claim for OT and keep copies.
Similar queries have been discussed in detail in other thread also e.g;
https://www.lawyersclubindia.com/forum/Company-trying-to-terminate-me--90855.asp#.UmummnCAqWM
https://www.lawyersclubindia.com/forum/Indian-law-similar-to-out-of-hours-working-banned-by-german-91026.asp#.UmumenCAqWM
It shall be appropriate to show all of your docs including job advertisement, job application, interview call letter, selection letter, offer letter, appointment letter, standing orders, attendance/OT record …………………………………etc to a competent and experienced labor consultant/service lawyer and proceed under expert advice.
The lawyer that has seen all of your docs can advise you the best.