Is A Interim MoU Valid For Recruitment In PSU Company

I am working in ONGC as Assistant Technician (A2 Level) since 2012 Asking Qualification for the post is 3 years diploma in engineering. It takes 18 years to reach E0 level from the A2 level. But my point- There is a Memorandum of Understanding between Management of ONGC and Recognized Unions, signed on 19 August 2004 approved by the Executive Committee of ONGC. but before MoU2004 there is an MRPR1980 for regulating the Recruitment and Promotion. according to MRPR1980, the induction of diploma engineers was A4. My question is that sir is it legal to recruit manpower by adopting an MoU instead of a full-phased R&P policy. We are very demoralized sir. It is a huge degradation. So please guide me on what can we do. Can we go for legal assistance? will it be fruitful?