Masters

Why didn't you do both. First do your UG and then PG.
Doing both from Canada will give you good output in your future and you will get a good job & good package easily.
If you don't afford both then it's better to do your UG from Canada. If you do your UG from a foreign country then it increases the

Yes Priyesh you can pursue Masters in Mass communication after B.Com but before venturing into it just probe yourself if you would be able to switch to the entirely different stream. If you have a flair for it and deep interest then only go for it.

Yes, you can get admission in IIM after clearing CAT/ GMAT and getting a good score in it.
To appear for CAT etc  student needs to have 50% in graduation. But eligibility criteria varies for various Management Institutes or Universities, they can take different %age in graduation along with these tes

For master's in eco u need Bachelor's in eco so it would be difficult to get admissions. Ignou take admissions with any Bachelor's degree so you must check with the university you wish to apply.

I would suggest youu to look into their skill shortage list and take the specialization accordingly.

Hi
You can explore their official website daad.de for all requirements and other useful information. For master's you require a good cgpa in Bachelor's, work experience and lots along with some publications/ research papers.