CBSE 10th

There are many institutes across India to prepare for the JEE Mains, but there are some coaching institutes in India which have only name and fame.
Kindly specify your location.

Class 10th board exams are Iron GATE for you, so you can have to give proper attention to board exams. When you are free from it then you can clear your basic concepts of class 10th and the main topic comes in JEE belongs to class 11th 12th NCERT syllabus.

The college which you will get depends on the percentage you got in 10th standard. There are no engineering or Diploma colleges in Chintapalle. To pursue Polytechnic, you have to go to Vishakhapatnam. Vishakhapatnam have good polytechnic colleges. There is also a Government Polytechnic in Vishakhapatnam.

You have a very good chance with your profile.

Hi Vikash,
You can go for CAT. But remember that you will not get an interview call from any of the top colleges including IIMs, FMS, etc. You may be able to get into one of the private colleges depending upon the cost score that you've scored.
Given that you have low marks in school and college, I would recommend that you study hard and get a good percentile - at least above 80, which can improve your chances of getting into a top tier 3, or a tier 2 college as well.

You have to arrange your lost certificates. You will get it if you apply for duplicate. Don't be tensed. You will get admission and certificates

It depends on your interests. If you are not able to find your interest then you can get counseled by any good counselor as that will help you to know your interests.

Hi Preet,
Yes, you can pursur your HSC or 10+2 in Canada. However, you have to check which all schools will accept international students which are mainly private high schools.