LLB

Hi,
The forms for new season will be out after March 2017. You need to score minimum 50% in your graduation to apply for DU LLB entrance exam and based on entrance, you will be further shortlisted. It does not matter, if you have done your graduation from correspondence. But, further selection you will have to be confident of why you are interested to pursue LLB studies.
All the best.

Yes, you can. You should opt for LLM through distance in Kurukshetra University.

Hi Dipankar,
To go for CBI branch, you can specialize in criminal law or else pursue forensic accounting course and go for CBI.
All the best.
I hope this answer is useful for you.
Kindly, feel free to revert.

You can pursue LLB after your B.Sc but it will change your career path totally.
You need to be very careful before you opt for this option. You need to pursue LLB and not LLM, LLM can be done after LLB .
Top colleges for pursuing law are:
University, Bangalore (www.nls.ac.in)
WB National University of Juridical Sciences, Kolkata (www.nujs.edu)
NALSAR University of Law, Hyderabad (www.nalsarlawuniv.org)
National Law University, Jodhpur, (www.nlujodhpur.ac.in)
Campus law centre, Delhi (http://clc.du.ac.in/)
UPES, Dehradun (www.upes.ac.in) - This colleges has further specialised courses in law, you can check their website

Following are the best colleges to pursue LLB: 1. Government Law College, Mumbai
2. Indian Law Society Law College, Pune
3. Symbiosis Law School, Pune
4. Bharati Vidyapeeth Deemed University, New Law College, Pune