Typically, visitors are allowed to stay in Canada for up to six months. The immigration officer at the port of entry will determine the duration of your stay.
If you wish to extend your stay in Canada, you should apply for an extension before your current visitor visa expires.
No, a visitor visa does not permit you to work or study in Canada. If you plan to work or study, you will need to apply for the appropriate work or study permit.
While not mandatory, it is strongly recommended to have travel medical insurance to cover any medical expenses that may arise during your stay in Canada.
If you are a citizen of a country that requires a visitor visa to enter Canada, having a valid US visa does not exempt you from obtaining a Canada visit visa. You will still need to apply for and obtain a visitor visa for Canada.