CBSE 12th

Absolutely, you can, but for that, you have to get a Bachelor's degree plus crack an exam which is conducted by your state govt. and you can also try for UPSE.

If you really want to become a PO in SBI or RBI, my personal recommendation would be BA because you will find all the subjects in the banking exam.
Which state do you belong to?

See commerce with IP is good which means you want to learn computer to its highest level, whereas, these two courses BBA & MBA are related to management field. Technology is in daily use, so for these two courses, basically, you should have good knowledge of computers.
1. MS-Word
2. MS-Powerpoint
3. MS-Excel
4. MS-Access, in some cases
5. Tally
6. Fast typing is a thing which everyone should learn.
And where about extra knowledge gaining in computers is good there is no harm in learning coding and creating software of general use.
As far I have seen, IP is the most scoring subject so it's good to opt.

Yes, your chances are good in new IIMs. Still you have to score 95 %ile in CAT exam and your PI.

Getting a job abroad totally depends on your skills, studies and dedication. To get a job abroad you can do your PG abroad. Then you would have better chances to get a job abroad. You can pursue B.Sc in India and then go abroad for M.Sc/MS.

You can create your own career in it right now with commerce (math). It is great no harm.

Hello Madhu,
If you have interest in physics, then you must do B.Sc in it and then M.Sc in Physics. Further, you can go for doctorate as well.