B.Sc

You can try for some private colleges or if the college you desire has a management quota, you can opt for it. I am not sure if they will accept your admission based on your credits, since the time has already paced forward and the annual term must have been started.
So, instead of wasting almost a year, try and contact the college and find if you can reserve a seat still.
All the best.

Tolani Maritime Institite in Pune is one of the finest maritime institute which guarantees 100% placement.

Hey,
You can make career in interior design if you have passion about it as it requires lots of dedication and enthusiasm as there are lots of opportunity and scope of this field as there are more prospects and this field of interior is growing with a boosting rate and if you are interested in the interior designing course then you should make survey of institutes, coaching classes and center for Ahmedabad as it is one of the leading cities in providing interior courses.

You need to be good in mathematics because after B.Sc + M.Sc, you can do PhD and can become a great mathematician. You can go for statistics also.

Yes, you can. But, if you want to go in business line then try to clear some basic business concept for your future understanding. If you want to do PGDM then search on Sikkim Manipal University because they have tie-up with some banks that they give you degree+training and bank will hire you 99% for at least minimum one year.

You should opt for physics.

The fee for B.Sc differs from college to college Kindly refer to the link below:
https://www.shiksha.com/search/?q=bsc&c=2&sc=64&sa=^^0^0^0^0^0&ts=1474416&rf=searchwidget

CSE is an all-round field. You can do much more in that.

It's very basic and high level understanding of ethical hacking, but to become a professional you need to get certified by CEH or CISSP.