Bangalore

You need to have some really solid reason to justify your bad grades. College admissions officers don't want to hear excuses unless the circumstances were absolutely out of your control.
Mostly all the colleges take into consideration your academics and extracurricular. Some may grant you admission on payment seat. But you need to really struggle to for good colleges with this percentage.

There is no provision to lower the MCA time duration for experienced candidates I.e. the MCA duration even for the experienced candidates will remain 3 years.

As per your marks, I will suggest to apply in Christ University and other government colleges in Bangalore. But, before getting admission, make sure about the placements of the college.

You must prepare for MHCET exam & try to get maximum % around 99.

I would suggest you to complete your class 12th first and then think about joining any institute.

There are no any MBA in construction projects management colleges in Bangalore.

Hi,
As far as know they have direct admission on merit bases. Eligibility : Graduation with 45%

Please refer to the link provided below for a list of colleges which offer courses for astrophysics in Bangalore. You can download their brochure for further details regarding admissions in any of these colleges. Normally, courses in astrophyics are scarce at Bachelors level, and you can specialize in physics and then apply for a course in astrophysics in the later stages of your education.
https://www.shiksha.com/science/colleges/astronomy-colleges-india