Poland

Hi Harry, the answer can be best given by yourself after you want what kind of career you seek for. Since, you are too young I will advice you to focus on your studies and study hard and complete your 10+2 with good academic grades. Know your aptitude. Check this you can understand:
http://www.salaryexplorer.com/best-paying-jobs.php?loc=173&loctype=1

Dear Ishan,
Poland is not a bad choice but Canada is one of the most popular and best. If you have a strong profile I will suggest Canada. You may further zero in based on your budget, climatic conditions and University admission requirements.

Yes, you will get salesman jobs (hourly basis) in departmental stores. Also, jobs related to delivery boys is also accessible.
All the best.

Yes, you can apply for the stay back card after graduation. More details can be found on the Poland immigration website. Generally, you can stay not longer than ten years on basis of stay back card unless you are qualified to become a PR. Please check Poland immigration website for this information.

Hi Soham,
Unfortunately, you won't have options as 49% is not accepted by any university abroad. 55% is decent enough. Look for options in India and maintain a decent academics before planning to study abroad. Understand that study abroad is not easy and if you don't qualify, they won't let you in.

Hi Soham,
Below 50% is not accepted. A poor ranking university can admit you but visa chances are low. In general, you must be qualified to study abroad and 49% is not an acceptable score.