While a 710 GMAT is generally strong and near the average at top-ranked programs, when you are compared with other Indian IT males with similar profiles you'll generally be at or below the average in that group. So as it stands now, while it sounds like you have some good teamwork experiences, international exposure, and start-up involvement, overall your profile is at risk for blending in with so many others. To have a chance you'll have to get noticed, by identifying what is unique about you and what you'll bring to the class. Perhaps it IS playing up what experiences you gained at that start up, or your teamwork and communication skills that are sometimes lacking among IT professionals, to make a generalization.
Among the schools you listed, I believe your best chances are at Schulich and Rotman. If you put together a strong application and essays based on what I mentioned above, you should have a shot at those programs. NUS and Darden are more of a reach but you could certainly try. As for scholarships and work permits, I unfortunately do not claim to have expertise in those areas but encourage you to do a lot of research online and through the admissions offices and career placement offices at programs you are seriously considering. Each country is so different regarding visas, and sometimes a company can apply for a visa for you, other times you get your own general visa before or separately from getting a job. And each school varies with regard to scholarships. Generally b-schools are not as known for scholarships, and those given are to the cream of the crop of the applicants so to speak; the majority of b-school students finance their education through low-interest-rate education loans paid back over time with their post-MBA salary. But it's certainly worth looking into.
Wishing you good luck in the process!
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