Exam

You need to complete UG and register for CAT exam.

Please get in touch with your institute for this query. Many colleges do not offer any exams after you have completed graduation while others may offer an improvement exam for a small fee.

Your GRE score looks good, but if you have 10 backlogs then probably engineering is not a good choice for you. You might be good at many other things, but certainly not engineering. Why do you want to pursue engineering only? There are many other higher education options in Canada which you can purs

It is totally dependent upon the career you want to pursue for the rest of your life.
Getting a management degree from an average college and then getting into managerial roles in corporate-sector, or, clearing banking exams and then securing positions like Probationary Officer.

CAT percentile to get selected in these institutes is on the higher side. Generally score around 98-99 percentile and above is required. Along with a good academic/work profile.