Science

Yes, job experience is required in most cases for IIMS. Your degree can be any though. But, being a B.Tech will be much beneficial in terms of prospects and growth.

Yes, you can get admission for B.Sc. Hons. with 70% marks.

There is only 60% chances that you can get admission in Andhra University, but surely you can get admission in affiliated colleges.

Both college make a clash in this sense but If you are looking for future studies in foreign then go for MU and KJSCE is autonomous institute, else P.U is also 10th in country and MIT also upgraded to autonomous this year.
If you live in Mumbai better go for KJS and if you are from outside both citie

Yes, you can sit for KVPY-SX. KVPY has two sections, each section has 4 parts or subjects, Biology, Physics, Chemistry and Mathematics. You can attempt any three subjects in the first section and any two subjects in the second section. If you are studying both, biology and mathematics, you can attem

If I explain, it will be so long. So, better go to UPSC portal. Download the exam pattern, syllabus. Whatever you need will be there.

60 seats are available in each department.

Just go through your chemistry basics- inorganic, organic and physical. You really don't need any special textbooks. From my own experience, I'd say Bachelor level chemistry knowledge is enough to crack the exam, plus general mathematics, logic and reasoning.