CA

Yes, you can apply for the same along with B.Com course.

In your case, you want to do 3 things at a time and for this I would personally suggest that you should continue with your CS and take part time courses along with that provides you with certificate and degree.

No, you can directly enroll for CA-IPCC right after your graduation. It has been made effective from April 2012. CPT is exempted for graduates. For more details, visit the website of ICAI.

Along with B.Com, you can pursue certificate in accounting technician course from ICMAI (CMA) or SAP in finance and accounts from a recognised institute. Thereafter, you will have good job opportunites in different companies if not, then you can appear for SSC, UPSC, and bank PO exams.

You should focus on getting a good job after completing CA. Salary depends on the kind of job you get and the firm in which you are working. After completing the CA course, you will get good salary package and numerous career opportunities.
For more details, follow the website of ICAI.

You may evaluate BBA and MBA, law, hotel management or fashion designing as an alternate to popular career options like engineering or medical.

For detailed information, you can visit the website of ICAI.

As exams difficultly level is concerned, there is no difference in CA and CMA. Yes, before graduation, you can enrol in level 1 i.e. foundation. After graduation, you can directly enrol in CMA level 2 i.e. inter. Follow the website of ICMAI/ICWAI to know the details of the procedure.