Hindi

Hi,
Yes, you can take Hindi as an additional subject. But, you should take mathematics subject, if you want to pursue CA as mathematics plays an important role in CA.
You can check the below mentioned link:
http://www.icai.org/post.html?post_id=3923
All the best.

Hi,
I think, you should go for B.Com honors. If you want to pursue MBA, then B.Com is a better option. If you want to go in teaching field, then B.Com will be beneficial for you.

You should not waste 3 years because of one backlog.

M. Laxmikant (Indian politics) is the best book for the same.

Generally medium of instructions of aerospace engineering is English in majority of engineering colleges in India. You may find some initial difficulties in pursuing engineering in English but you can overcome these difficulties. I was from a Hindi medium educational background but could easily do BE, M.Tech and MBA in English with bit of an extra effort.

Dear ,
For the opening you need to check with the respective HR deptartment but for every process BPO require good command over English . Suggestion from my side improve your communication first and than apply for good profile in BPO KPO or MNC
You can check British council for English communication programme through that you improve and feel confidence too.
https://www.britishcouncil.in/
All the best

BCA is a technical course, so it is better if you are doing BCA in English because in BCA you need skills in English.

Yes, you can apply for IIM - C. But, you will have to clear an entrance test followed by the personal interview.