Can a Employer pay less salary then agreed in Offer/Appointment Letter

Hi All, I am having 10+ years work experience. I had Recently joined a Pvt. Ltd. I.T. company (its my 5th month going on) . I have Received a Appointment Letter From Company in that they have mention X amount as Salary, After 2 month the BOSS, one day suddenly he called me in his chamber and said he can afford the salary blaming me of not giving performance and he will revise my salary, I clearly refused that I can not work on Reduced salary ( he said that in verbal only, no formal letter or E-mail ), he then said we will sit with HR (her wife doing role of HR, she only comes 1 or 2 hrs. daily) and discuss on this and finalize the things. After that many days passed but he did not sit for further discussion, I many times asked for the same both to BOSS and HR for same but every time they given this and that excuse and they passed about 20 days in same. After around 20 days Boss again called me in his chamber (after my many reminders verbally for the due meeting). and again he started saying the same, I told him I Already told you that i can not work on less salary and i am saying you from so many days to finalize the things, then he suddenly told me that i had already told you that i can give you only 60 % of the X amount, you thing and reply me accordingly, but he had never said that earlier, earlier he had only said that we need to revise you reduced salary, so we will have a meeting with HR and finalize it soon, but that never happens till now, I Clearly said that I will not work on less salary, then he said ok Complete the ongoing projects (3 projects i was working on that time), and i will relive you, now yesterday again he called me for meeting (after my so many request for same), he told me to send a resignation on email to HR and then we will discuss and decide the Exist Policy (they have 3 month notice period), he him self told that though we have 3 months notice period , we will not have that in your case and after i mail my resignation then he will call me again to have final meeting with him and HR for the no of days for notice periods. and Still he haven't paid me for the month of Dec and Jan and for First 7 days of September (my Joining date was 24 September 2020.) Kindly let me know what are my option to get the Full Salary on X amount for the time i have served the company, and kindly also let me know does any private limited company has any way/right to not give the salary agreed in the Appointment letter. Thanks in Advance.