Science

Yes, if you want to get admission into top universities and colleges for BCA then you definitely should study mathematics in your 10+2. As the eligibility criteria for these universities requires maths as a mandatory subject to be eligible for the admission. Also, you'll be studying maths in BCA too, which is reliant on the maths taught in 10+2, so it'll be beneficial for you to study maths already in school and build your base stronger. So, you don't have to work harder later in college. Even if you did pick maths as a subject, then also you're eligible for admission into BCA but not in top universities.

Every time this is not true !

Yes, to be eligible for MCA a candidate needs to have Maths as a mandatory subject either in +2 or in graduation, which in your case is already satisfied. To be eligible for MCA you need to score at least 50% to 60% in graduation.

BCA course is primarily meant for non-Science stream students to get into IT. As Science stream students can pursue CSE or IT. So, yes Science stream students are also eligible for BCA but your primary focus should be to get into B.Tech (IT), as you'll have much more opportunities as compared to BCA student. If you do not have interest in Science anymore or you're looking for much easier course, then BCA is perfect. As the study load in BCA is far less as compared to B.Tech (IT).

Hello,
IIT JAM is an online entrance exam conducted by IIT every year in a month of February to get admission in M.Sc and Integrated Ph.D courses in different IITs, NITs, IISERs, etc. Online process to apply for IIT JAM exam is started. You can apply for this exam by filling online application form.

Hello !
Post in ISRO is depends on availability of seats, recruitment criteria etc. Of ISRO !

Hello,
It depends upon recruitment criteria, availability of seats etc. of ISRO.

Hi,IIST provide only B.Tech, M.Tech and Ph.D degree.