Non-Promotion due to Change in promotion policy

I was recruited by NHPC Ltd. as a Trainee Engineer in 2014. At the time of my appointment, the promotion policy stated that promotion up to the level of Senior Manager-E6 ( Then called Manager (E5) ) shall be in time time-bound manner. There was no interview and no restriction or vacancy-based promotion. In 2022, the company changed the promotion policy and introduced restrictions in the form of percentages, i.e., for promotion from one grade to the next higher grade only a fixed percentage of executives shall be promoted from the eligible executives. For example, for promotion from E4-E5, only 60% of the executives of the eligible executives shall be promoted. Also, the interview was introduced with a weightage of 15% (15 marks) with minimum qualification marks in an interview (06 marks for reserved and 07 marks for unreserved category candidates. Now what is happening is that, despite serving the corporation in rural and far-flung areas, and getting very good marks in the last 05 APR, I was disqualified after a 5-minute interview. There is no recording of the interview, no records of questions asked and answers given. My query is can a PSU change its promotion policy causing loss to employees and which was not in effect at the time of his or her appointment? and if Yes how justified are the Interview criteria that seem to be adopted for eliminating candidates? Will my case have merit in court if I file a case?