CBSE 10th

You should pursue PCMB to become a diabetologist as it requires a science-focused Bachelor's degree and a Doctor of Medicine. Apart from that, it requires an internal medicine with a sub-speciality in endocrinology.

To get admission, you need to give CAT, MAT, XAT, CMAT or ATMA and then final selection will be done via a GDPI (group discussion and personal interview). These are the main and most important exams to crack not the UPSEE. However, a good score in the UPSEE will definitely help.

I am trying to apply to NUS. I have seen the application of NUS for 10th, it asks for your English marks only.

While most institutes follow the system of 10+2 which means you need to pass your 12th grade. There are some institutes that would allow you to join after passing 10th grade itself. However, for gaming colleges there is no requirement of minimum marks except that you must past 12th grade. Therefore it is advisable to complete your schooling and pass 12th grade.

If you want to do Diploma in engineering then you don't need to give CET as your admission process is going to be on the basis of class 10th percentage.

After 10th, you can do class 11th and 12th in science, commerce or arts. You can also dop Diploma in engineering.

If you want your brother to do fashion design than he needs to complete his class 12th followed by Diploma in fashion design.

For getting admission in XLRI, you need to take XAT exam and you need to clear their cut-off as well.

No, the cut-off for FMS is more than 99 percentile so if you want FMS then you need to score more than 99 percentile.