Reagrding Changes in RR during the course of recruitment

I am internally recruited and promoted as Management Trainee(MT) in BSNL vide notification dated Nov-2018, as per MTRR-2013, examination was held in Feb-2019 and the result had got stayed due to case by aggrieved senior batch officers at CAT Chandigarh. The stay had got vacated in June 2022 and after GD and PI, we joined in June-2023. As per MTRR-2013, the MTs were recruited as per Management Services RR-2009 to provide fast track promotions up to GM/CGM. But in January-2023, BSNL has amended the MSRR-2023 and snatched the fast track promotions opportunities of MTs. When we came to know that BSNL was amending the MSRR then in Dec-2022, we approached CAT JBL and CAT JBP restrained BSNL from making any amendments in MSRR-2009 till the completion of MT recruitment. During our joining BSNL had forced us to submit the undertaking that we are accepting MSRR-2023, as without this undertaking BSNL was not giving us joining letter. Now please suggest what is the best legal remedy available to us for getting MSRR-2009.