Science

Hi, yes you are eligible for CAT. You just need to do a planned study in math since you feel you are weak in that subject. Being an experienced person in the same field I would like to suggest you to solve practice question papers as many as you can, this will help you in scoring and accuracy in your answer.
Good Luck.

You have to choose that stream in 11th according to your aim or area of interest. If your aim requires need of chemistry, it would mean that you want to pursue something technical field. You must opt for PCM in 11th in that case. Give more time to chemistry than other subjects. Work hard on it and do regular studies. Or if your aim does't relate to technical field, then you can opt for any stream like arts, commerce, etc. For any query, please feel free to ask.
Wish you best of luck!

MCA course is more better than M.Sc. Computers to become a software engineer because both are good but MCA is a professional course and you have to in a corporate world. So, I prefer MCA.

Yes, you can pursue a course in life sciences, but you need to decide which level of life sciences course you are going to pursue. Depending on the education level, students can enter the field of research, teaching or medicine. An undergraduate degree, preferably a Bachelor of Science in Biology, is required for entry-level jobs. A graduate degree is needed for research intensive position. A master's or doctoral degree is needed are research or teaching positions. Regards.

If you want to become a nutritionist, B.Sc in Nutrition should be the viable option for you.
How to become registered dietitian in India?
Educational qualifications required: B.Sc. in Home Science (Food and Nutrition) or B.Sc. in Nutrition and Dietetics or other relevant B.Sc. course. After B.Sc., one must also complete M.Sc. or PG Diploma in Clinical Nutrition or Food & Nutrition.
After completing relevant B.Sc. and M.Sc. courses, one must go through 6 months long internship stint at any one of the many hospitals recognized by the IDA OR possess 2 years work experience at any multidisciplinary hospital as a dietician. Regards.

The test will be conducted in the month of June-July.

Yes, you can apply as you need to have passed 12th with minimum 50%. .