It's up to the college, but if you can
convince them maybe, it's a big ask. I would act as fast as you can
and don't mess them about at all than you can change the course in
the same college (if seats are available there) otherwise you can
also change the college.
Yes you can , if your college gives an option or your selected subject must have the options. In courses like Engineering and BBa there is an option .
Yes, All colleges allow you to change course with in a couple of weeks of the start of the course.