If a person enters Canada with a student visa, can he use platforms such as amazon or shopify to earn money while studying, or can he work in the field of digital currencies and have his own business and income besides his studies? If he can have a lot of income, won't there be a problem?

The answer to all these questions depends on the work permit given in Study Permit. Depending on the conditions, this work permit can vary from none to 20 hours per week. It is not necessary that all 20 hours are for one employer, so you can work for yourself or for several employers, as long as it does not exceed 20 hours