B.Sc

Dear Ria,
Since you have done you graduation in Statistics and you are showing interest in Analyst, I hope you are willing to be the 'Data Scientist'. For this you not just need Masters but also Doctorate required. Yes! MBA in analyst from Amity 'Noida Campus' is good. But be consisting. Because this is the feild where only dedicated students can find the success. Hope this helps. Upvote the answer if you feel satisfied.
Good Luck.

Yes, you may get B.Sc. Life sciences in DU, but not in the top colleges. I guess in the very first or second cut-off list. But you can surely get it in some lower colleges.

Please check for your eligibility to apply for the JECA exam from the criteria mentioned at the link provided below:
https://www.shiksha.com/it-software/exams/wbjee-jeca
WBJEE JECA 2018 Summary:
JECA or Joint Entrance Examination for admissions to Master of Computer Applications MCA is conducted by West Bengal Joint Entrance Examination Board (WBJEEM). The exam is a gateway for admissions to MCA courses offered by colleges in the state of West Bengal. Regards.

Mostly admission to this programme is based on the percentage of 10+2. However, some institutes in the country offer the course based on the candidates performance in a relevant institute-specific entrance test. So you need to decide on the college in which you wish to apply and check there eligibility.

UPSC demands you to know all the subjects from history to biology (both for preliminary and Mains). So I would advice do not choose your graduation stream only based on being UPSC aspirant. At the same time make sure you read news papers daily, specially The Hindu. The last three year paper trend has been based only on current affairs question. Read all the NCERTs from standard 6 to 10, and geography, history and political Science NCERTs of standard 11 and 12.

Well, that depends upon the college you wish to switch and whether your college allows migration to the other college. So, please check the same with your college once and the other college you wish to take admission in.