Career

The easy way is first one as a diploma will be completed in a year or two and then you can apply for PR. It will also allow you to work. If you already have bachelor's, you need to register at pebc. Check for all details here.
http://www.pebc.ca/index.php/ci_id/4910/la_id/1.htm

It s very difficult to identify which course is best for making into IAS list of Civil Services. You are advised to chose subjects based on your interest and past performance( Subjects in which you are sure to achieve acedmics excellance).

Hi
For Master's at IIT, you need to appear for IIT JAM and GATE is also accepted. For abroad, you must have GRE/GMAT score and IELTS/TOEFL. Rest of the requirements will be as per the country you choose to apply. You may go for M.tech/ M.E / Mba abroad. For USA, take a look here.
http://www.masterstudies.com/Masters-Degree/Engineering-and-Technology/USA/

Petroleum engineers have opportunities for job at offshore on water rigs as well as oil wells in plains in oil/gas exploration. Petroleum Engineers are also have equal or more opportunities for employment in Petrochemical plants.

Hey Sundaram,
You should take admission in B.Tech CSE. Along with this select a university which emphasizes on practical knowledge and industrial experience. Meanwhile you can also visit websites like coursera, edx etc. Some best universities suggestions -

Dear Divya,
With this combination you can go for these fields :
Physics / maths hons
Environmental Science
forensic science
Geo-informatics & Remote Sensing
Mca
Nanoscience
Actuarial science
Now you can search on this fields and choose accordingly.
All the best