Colleges in Mumbai

Hi Arnold, St. Xaviers College doesn't offers MBA degree, rather it is Xavier Institute of Management and Research which offers MS (equal to MBA):
https://www.shiksha.com/mba/course/master-of-management-studies-xavier-institute-of-management-and-research-ximr-fort-Mumbai-113330
Kindly visit this link for more details.

The required SC category cutoff is around 85-93 percentile.

N. L. Dalmia Institute of Management Studies and Research offers Post Graduate Certificate in digital marketing and social media analytics. It's a 480-hour programme providing aspirants with a unique combination of interdisciplinary coursework and cutting-edge research. For more information you can visit - https://www.nldalmia.org/pgc-in-digital-marketing-social-media-analytics/

Yes, you can do BA honors in applied psychology from Amity University.

I would say it will be better to complete your intermediate first, as that would be beneficial in the long run.

If you hold a Master's degree in Biotech, you are eligible for most of the research jobs but a preference is given to candidates who have qualified any of the national level entrance exams like CSIR NET, GATE, DBT, BET, ICMR, JRF and NET. However, do not get demotivated you still have a lot of scope without them. You have the following top options after M.Sc in Biotech:
Go for a Ph.D.
Apply for a corporate research job and start climbing the corporate ladder (this part is tougher than the entrance exams mentioned above).
Go for Teaching / Academic jobs.
Get into Marketing & Business Development.
Get an MBA degree.

It is good, gives many opportunities and the events which are held there are memorable always, good faculty and descent placement.

NMIMS-Navi Mumbai is better and reasonably good to study at.