CBSE 12th

Hello Abhi,
For getting into top notch product based companies like google, Microsoft,& cisco, you need to do to get into very good colleges like IITs, NITs, IIITs and BITs Pilani to increase your chances to get placed into these, otherwise its very tough for you to get into these companies you have to be your own.

First of all, you need to be a science student for pursuing engineering and you can do B.Tech in CS even if you don't have CS in 11th-12th.
Good luck.

You have just completed your 12th. So first try to focus on your graduation and start focus on CAT in between last 2nd year or final year of your graduation.
TIME, IMS or CL are the best coaching institutes.

You can go for B.Com+CA, B.Com+MBA or BBA+MBA.

Please visit the given website:
https://www.quora.com/What-are-courses-available-in-chemistry-after-12th

If you have passed class 12th with Science and biology as a subject then you can pursue B.Sc. in Forensic Science. For UPSC, it will help you in biology subject. You can also apply for other positions and vacancies whose exams are conducted by UPSC.

PUSA admission is dependent on your NCHMCT rank.