Legal advice - Job dismissal after wokring for 22 years

1. I am working for finance company and is at a senior level managerial position 2. During last 6 months the performance of my department dipped due to non-replacement of a resource in a small team, despite my repeated request for immediate & dedicated resource. I have been slogging for 11 hours a day on an average in addition to working weekends. 3. Only 3-4 months back, a resource was provided who was not reporting to me but to my manager. And post that I was starting completely ignored, no invite for any meeting and had to undergo humiliation whenever at every escalation. I was made to do all kind jobs meant for juniors. 4. Because of enormous work pressure I started having bout of depressions & doctor advised me to take 3 weeks of medical leave. 5. 2 months back, I sent meeting request and wrote male twice to my HR and my manager to clarify as to why I was not given any increment. I was asked to fix meeting twice but meeting was rescheduled and never happened. 6. Few days back, I received a meeting invite from my manager to have a discussion with our HR manager. I enquired the agenda of the meeting which could be answered after multiple follow up on phone/ mail & I was told very briefly that it is mid year feedback session. 7. During the meeting I was grilled by my HR manager in the name of feedback who was on call from outside. I was asked what improvement effort have I done when the process was stable to take care of such scenario to avoid my process from derailing. HR manager was asking detailed questions of my process as if he is my functional manager. He was behaving like a "Dada" and went to the extent saying " Chal resource to nahin milega, ab bata kaise performance dikhaiga". I was repeatedly made to answer on my performance improvement plan without required support. I repeatedly tried to explain my grievance but response from both was full of arrogance And by the end of the meeting my manager alleged by saying the biggest problem is my attitude and concluded by asking me to tell what is the relieving period I may seek, in case I need any consultant number or any other HR related help, they are more than happy in helping me. 8. Please note current management took over last year from an MNC and prior to that whenever retrenchment happened, employees were given compensation equal to 15 days of salary for every completed year. Earlier management had monetary agreement with new management to ensure none of the employee should be sacked within 1 year of takeover. My questions: 1.How dip in performance for 6 months becomes an issue & causing dismissal after working for 22 years(in 20 appraisals my rating was either strong contributors or better) 2.How can I put forward my grievances to senior management when HR and functional manager has already told me to go? 3.What is the legal remedy for me and what compensation I can seek looking at the agony I am going through and more so when 1 year guarantee is over