Class 12-science

Pharmacy would be the best option other than engineering which can provide good jobs with best salaries.

Chemistry, like other math-heavy fields in the sciences, is a subject which requires hard work and effort to master. Chemistry entails equations, formulas, and diagrams; some of these may have to be memorized, while others require a complex understanding of chemical structures and math equations. To excel in chemistry, you'll need to practice good study habits and pay attention during the lecture, lab, and while doing homework. Chemistry demands a lot of patience, enthusiasm and most importantly, a good relationship with the subject.

Hello Ashish,
In India, course in paleontologist is available only at PG level. Offered by geological survey of India in Hyderabad, you can do graduation in Geology or biology and then PG. I am attaching a link that will give you all the required information.
http://entrance-exam.net/paleontology/

Go for graduation from Delhi University. Admissions are based on class XII merit.

Diploma is not compulsory for doing B.Tech. 12th science along with JEE Mains is compulsory for doing B.Tech.

You have a lot of good opportunities. Science has a lot of options to go in for:
Architecture
Engineering
Medical
Pharmacy
Dentistry
IT
Computer Science
Botany
Aviation
Physics
Fishery Biology