Dear Paras, if your question is how to study CA as a PG course, first things first, CA is not a Post Graduation course. It is a Professional course which can be studied at 3 different levels like CA Foundation (10+2), CA Inter (Bachelor's degree) and CA Final. So if you pursue any degree in Bachelor's you can opt in directly for CA Inter. If you are a Commerce Graduate you need to score a minimum aggregate of 50% for being eligible for Direct entry to CA Intermediate. For Non Commerce Graduates, it is 60%. So you can study any Commerce subject in your Bachelor's score 50% and be eligible for CA Inter directly.

Dear student after you complete 12th standard you should go to graduation in b.com because many course you may study and your career scope large like.
Chartered Accountant (CA) ...

Masters of Commerce (M.Com) ...

Masters of Business Administration (MBA in Finance) ...

Certified Management Accountant (CMA) ...

Chartered Financial Analyst (CFA) ...

US Certified Public Accounting (CPA) ...

Financial Risk Manager (FRM) ...

Association of Chartered Certified Accountants (ACCA)
Thank you..