Nc-obc eligibility

Dear Sir/ma'am, Date: 02.05.2018 The below case is presented on behalf of my friend. He has NC-OBC certificate signed by Sub Divisional Officer on dtd 05.09.2015 and having a validity of 3 yrs i.e. 31.03.2018.He has applied for MBA admission and the same certificate is verified & passed at the time of document verification during a personal interview. However, as per the offer letter from some colleges & CAT admission committee, they need NC-OBC certificate having a validity of 1 year and valid in FY 17-18. Now the fact is that my friend is working in MNC and his father is working in SBI at the post of Special Assitant, age 50 yrs. The income limit of his father has crossed 6L as an average for last three financial years. We are having doubts about following points, 1. As my friend's father is a servant in SBI, PSU, what are the criteria for issuance of NC-OBC certificate? 2. Will it be ok/allowed to issue non-creamy layer certificate on the basis of my friend's income? Average for three years comes out to be approx 4L?