B.Com

Dear Prashanth,
You have not mentioned how many backlogs and what was your final year percentage. A few backlogs are okay and the pass percentage should be above 65%. You need an IELTS score of overall 6.5 with no band less than 6. You do not need your GMAT for Australia and you need the your academic transcripts, 2 letters of reference and a statement of purpose. The exact academic requirements will depend on the University you are applying to and will be given on their website. Ensure that you enrol for a 2 year duration MBA as anything of lesser duration will not get you post study work visa or points for PR.
All the best.

Yes, you can pursue B.Com after class 12th.

According to Indian education act-1959, you can not pursue two degrees simultaneously, because it causes extra burden on students (according to law makers). But after the recommendation of few universities, UGC has now granted the permission for students to get enrolled in two degrees (in same or different universities).

After B.Com, it would be better.
Nevertheless. if your keen interest is in pursuing law as your career, you should go with that rather than what everyone's doing now.
Got more queries? Kindly revert.

Dear,
As per your query, you can think of these programmes:
Actuarial science
Public policy
ACCA certification
Project management certificate
Development studies
MBA (Media Management or Hospital administration)
All the best.