Replay to Absconding letter

I was working with IT co in QC since last 10 years who offering services to Banking Indust. During Covid 19 pandemic I was working from Home for 2 Months. During this period I didn’t assigned any task from my Reporting Authority. I have responded to all issues forwarded by Implementation Team. The co also paid the salary for 2 ,months. After that in June 20 I received a mail from HR stating that I have failed to perform task assigned to me and are off duty since 03/20.I have not taken any approval for not to working. I have also not been attending office premises for performing assigned tasks. HR asked me to resume the work by attending office with immediate effect to avoid any further loss in productivity and loss of revenue. I denied all allegation made upon me. I asked HR to give me the list of task assigned to me which I have not completed. Hr failed to provide the information sought by me. I replied that calling me to resume office during nationwide lockdown is unfair and violation of advisory of the government in COVID-19 pandemic. Only essential activities are allowed in containment zone. I attached Order issued by the MHA ,GOI dt 30/05/2020 and asked HR to confirm that my work place is outside the containment zone. I will resume work by attending office as soon as lockdown restriction lifted by the gov. Then I got reply from HR that Co was permitted to function by MHA under the notifications issued earlier and even issued now since we cater IT & ITES services to the Banks. Hr asked me to report at another office situated in suburban which was Administrative office and no QC related activities are performed there. Hr has not provided me the details of my new Reporting Authority. Hr warned me that In case you fail to provide details as sought and resume work as called for, the same shall be treated as leave without pay.I simply ignored the mail as it was nationwide lockdown and no transportation was available. After some days co disabled my co login and restricted me to log in and respond the mail send to me. I have responded to all issues forwarded to me on my whatsapp No till Sept. 2020. There after no issue was reported to me. The Co has not paid me any salary from June 20. On 24/01/21 Hr dropped a mail on my Personal ID stating that I have failed to respond the calls and emails and absconding from service. Neither I am working from Home or contacting senior manager or office. Hr declared me absconding and terminated my service with immediate effect. HR has not served me any Legal Notice till Date. If I resigned I have to serve notice period of 90 days or option to buy out which is mentioned in my last appraisal. My next appraisal date was 31/12/20.I am not interested to continue my job in the said company but as they have marked me as absconding my career is in danger and I can not grab new opportunity till I get release letter from the co. I cannot bear heavy expenses of legal proceedings, pls advice what I should do in such case