Hello,

First of all let me tell you BA-LLB is an undergraduate degree in law for which the eligibility criteria is based on 12th educational qualifications, on the other hand LLM is a postgraduate degree in law for which the eligibility criteria is law graduate whether it's integrated law programs such as BA-LLB/BCom-LLB/BSc-LLB/BCA-LLB/BBA-LLB etc, or LLB for a duration of three years which candidates can pursue after completion of graduation.

Next, to become CBI Officer you can appear for UPSC, and join Indian Police Service to become a Group A Officer in CBI, another route is to become sub-inspector in CBI through appearing in SSC CGL, in both these exams the eligibility criteria is simply passed graduation in any discipline from a recognized university , to answer your question if you intend to appear for UPSC/SSC you just need to pass graduation in any field, it can even be simply BA/BSc/BCom also, but if you're interested in law field it's better you pursue after 12th standard only, the integrated course is for five years, you don't need to pursue any sort of post-graduation in any field in order to appear for any of these exams, the reason being the eligibility criteria as laid out by authority simply states candidate to be a graduate from a recognized university, there is not even specific aggregate requirement in either of the case.