Class 12-science

To get admission on the basis of 10th, there is only one thing, Diploma or ITI. But these will take another 3 years and after then you can take admission in B.Tech and other courses.

Your future doesn't get blocked, if you scored less marks in boards, you've all the options to go for as per your interest but as per my suggestion opt something different that has better employability than others some of these are:
1. If you've degree in mathematics then go for actuaries, apart from pursuing graduation.
2. Law.
3.B.Com/BBA and do financial Modelling course with them.
4. Interior designer.

I have no more knowledge about Science stream. But, as I heard the PCB students doing Pharmacy. You can do Pharmacy, and also please ask your friends, teachers, parents, relatives, neighbors.

Class 12th is compulsory for Pharmacy.

Yes, you are eligible for B.Sc in food technology as only 50 % is required for eligibility, but for admission in any college it depends upon cutoff.

Chhaya Prakashani is a better option. Chhaya Prakashani Books, for all the four subjects including Physics, Chemistry, Mathematics and Biology. These books also helped others for the preparation of WBJEE and JEE Mains. Since it includes all the topics according to the syllabus (for both WBCHSE and CBSE ), more pictures and diagrams. And most importantly it contains previous years papers ( WBCHSE, NEET and JEE Main with solutions too.

If you want to do B.Sc in agriculture from Government College, then there is an entrance exam for this i.e. PAT. So, if you want, then first you have to go through this exam.

You have to clear your Diploma degree and then you can take admission in engineering.

The NEET examination is a medical entrance examination and UPSC is an examination for civil services for now, you should prefer NEET after 12th Science.