Delay And Denied Appraisal After Termination Of Service

I started working in an MNC (Tech company) on 24th November 2017. Due to their policies, I got only one increment till 2019 and that too was not consulted with me. I reported this to HR but HR said that the appraisal process is closed and should inform them next year if this happens again. In Feb 2020, I was released from project and spent 3 months on the bench & in May I was asked to resign as acc. to company policy I had to remain unassigned for 90days. To which I agreed, but I waited for May's salary as the yearly appraisal is usually completed by May. But that didn't happen. I called HR, and he said the company has decided to shift appraisal to Q3 of 2020, and employees leaving before would not get any increment. Thus increment is pending as of April and since they are asking me to resign, they should pay me an increased amount of Apr, May. Please help me if I have any legal option here to get my increment. FYI: Currently I haven't resigned, I have 1 week left. And then I'll get 3 months advance pay