LLB

CS + LLB are core qualifications that can shape your career in the direction of secretarial, legal, corporate governance and corporate and securities laws. Since you are pursuing these qualifications already, am assuming that this is your ultimate goal.
FRM is no doubt a very competitive qualification with an abundant scope and market demand. However, you need to understand that FRM is a qualification solely based and focused on risk, not even financial management. Are you sure you want to specialise in risk management and the sorts? If you do, then CS + LLB is of no use and FRM would be the ideal choice. Although the syllabus would be quite different and so would the approach. Yes, it looks very impressive on your CV but it will have no utility in the field of FRM. Vice versa, if you are pursuing a career in the legal, FRM is hardly useful.
So to sum up, it'll look good on the CV, but will have no use.

For the purpose of LLB (Hons.) (Three Year/ Six Semester) course admission, the Banaras Hindu University conducts Undergraduate Entrance Test (UET), during 3rd /4th week of May every year. Admissions are done according to merit in the UET, subject to fulfilling of eligibility requirements mentioned below and availability of seats.
Minimum Eligibility for 3 years LLB at BHU is as follows: BA/ B.Sc/ B.Com./ Shastri (at least 10+2+3 pattern) securing a minimum of 50% marks in aggregate considering all the subjects in the three years except those subjects where only pass marks are required and which do not contribute to the total in the final (degree) mark sheet. OR any other Degree under at least 10+2+3 pattern recognized by the Bar Council of India for the purpose of admission to LL.B. Course securing a minimum of 50% marks in the aggregate considering all the subjects in the three years.
You are eligible to appear in LLB UET conducted by BHU based on your educational qualification.