Civil Servant (IAS/PCS) exams

Yes, you can appear UPSC CSE after BSc Life Science. It will be helpful if you opt life science as your optional subject in UPSE.
All the best. Feel free to revert.

arhiamt books and daily newspaper

yeah it will come

NDA is for Selection and Training of candidates for Commission in three services of Indian Defence. Once you are commissioned you can not appear for Civil Services unless you resignation is accepted by President of India. If your resignation is accepted then you will have to refund all training expenditure incurred on you by Government of India.

Hi Dear,
Basically Interview is to access your intellectual talent. They won't focus much on your 12th or Graduation Score. If you haven't done well in 12th, there is nothing to worry.