M.Sc

You can do PG in mechanical engineering from these colleges;
Durham College
George Brown College
Sheridan College
Algonquin College
Humber College
Seneca College
Centennial College of Applied Arts and Technology
Confederation College of Applied Arts and Technology.

In my opinion if you pursue M.Sc from a good reputed university where placements are offered and if you have skill then you can definitely get a job in a pharmaceutical company. Currently the pharmaceutical sector is on boom.

Choose what you love. Also look at the curriculum and the university. Pursue career in microbiology only if you get admission in a good and prestigious institute. Zoology is a core subject and hence offers a wide range of career opportunities whereas microbiology is an specific course. Although there are bright opportunities in microbiology but look for some good institute.

Refer the following:
Dr DY Patil University, Tilak Ayurved Mahavidyalaya, Bharati Vidyapeeth, Yashwant Ayurvedic College etc.

Refer the following:
IMS BHU, State Ayurvedic College and Hospital, etc.

Refer the following:
King's College London, University of York, Cranfield University, University of Bristol.

Refer the following:
Uttaranchal Ayurvedic College, Uttarakhand Ayurved University, DIMS Dehradun

Refer the following:
VIT, BIT Mersa, Jain University, Amity University, Jaipur National University, Ganpat University, Adamas University etc.

Yes, definitely you can do MS in CS from abroad.