NIOS 12 th

Hi Dev,
You need to check college websites or visit their campuses for admission notifications. Every college will also have their cut-offs and entrance depending on the course. You can refer to the course list below and filter out colleges in Mumbai based on your course interest and go through the process and eligibility:
https://www.shiksha.com/bba-chp9

Hi Arindam, please check it on their website, here is the link for their syllabus:
http://www.nios.ac.in/online-course-material/sr-secondary-courses.aspx

Eligibility for BEC is based on your EAMCET rank according to your stream.

Hi Ranveer,
You can do B.Sc or Diploma programs, you will be eligible for lateral entry into most of the B.Sc programs provided you meet the academic criteria and clear entrance exams if any. Know your interest, your likes and dislikes, figure out what kind of job you want to do and choose your course.

If you are serious about pursuing Law, you should try to apply to full-time proper law schools.

Dear Dev!
Many of the private college don't consider NIOS Student for their regular course. So firstly you need to contact the college administration asking your eligibility. If you are eligible, then the procedure is same as like of any other board candidates.
Hope this helps.
Good Luck.