M.S

You should definitely go for:
1. TOEFL.
Tata McGraw Hill – Kaplan.
2. GMAT.
The Official Guide for GMAT 2017 - The Princeton.

Dear Khurminath,
Germany is the best country for mechanical engineering but your academic grades are not at par with German universities. USA on the other hand has the maximum universities which are globally known, you can check out university options in US, Australia and UK for your studies.
Remember to study in US you must take GRE. You must also take a look at the entry requirements for all universities you wish to apply to as they differ.
Best of luck.

Hi Anmol,
Kindly, refer to the program page to know about the admission pre-requisites, I am listing out the helpful links here, for further clarification please write to the university.
https://www.ethz.ch/en/studies/registration-application/master/programmes.html
https://www.ethz.ch/en/studies/registration-application/master/application/admission-prerequisites.html
https://www.ethz.ch/en/studies/registration-application/master/application/admission-prerequisites/requirement-profiles.html

Yes you can provide your IELTS scores for admission purposes, but check with the university website once if they accept IELTS scores or not. Most universities do accept them, so you should be fine.

You don't need to pursue any additional diploma to study MS. Your undergraduate years count for the required years to education. Many Canadian universities and colleges accept 15 years of education, so check the eligibility requirements of your course on the college website.

Yes, you can get admission, provided you have strong TOEFL and GRE scores. You can apply to Harvard, Yale and Stanford, universities.