My company terminated me immediately effect with wrong allegations

I have been associated with the company since 2011 and have been a top performer in all my roles, reaching the level of Head of Department. My company made several commitments, such as providing ESOPs and changing my salary and designation, but there was no progress on these fronts. Consequently, I requested clarity from my manager. However, a week later, my HR informed me that due to poor performance, they were asking me to resign. I requested evidence of my performance issues as I had received a salary increase just 10 days prior, which came as a shock. Despite my 13 years of service, they terminated me abruptly, cutting off all access. They mentioned in mail i am none supportive and didnt pick call on Teams so they have terminated me on immediate base. All this happened just within 15 mins. After repeated attempts to contact HR, they agreed to a smooth exit if I resigned, which I agreed but i ask was please revoke termination then i can resign. However, they changed the terms, stating that the reason for separation would remain the same, but they would support a smooth exit considering my long tenure. Confused by their actions, I reached out to HR, but they provided conflicting information orally and refused to provide anything in writing. They demanded the return of office property, which I had already surrendered, and pressured me to submit a resignation from my personal email, but they refused to revoke the termination. When I protested against their unfair treatment via email, they accused me of making baseless allegations against the company and terminated me, issuing an experience letter stating termination. My career has been severely affected, and despite a 90-day notice period, they have not clarified the terms of my notice period pay or gratuity, only mentioning legal proceedings. On May 1st, I received some money in my account, but I am unsure of the basis for this payment or how it was calculated. Additionally, my food card was only loaded for 23 days. I am experiencing severe shock and mental trauma and need guidance on how to fight for my rights in this situation.