Hi
1. Actually that answer is wrong. If you have a valid visitor document (work/study) as long as you only visit the Continental US or St. Pierre et Miquelon, you don't require a TRV to re-enter Canada within the validity of your visitor document. .
Visa exemption — purpose of entry Dispense : objet de l’entrée
(3) A foreign national is exempt from the requirement to
obtain a temporary resident visa if they are seeking to enter
and remain in Canada solely
(f) to re-enter Canada following a visit solely to the
United States or St. Pierre and Miquelon, if they
(i) held a study permit or a work permit that was issued
before they left Canada on such a visit or were
authorized to enter and remain in Canada as a temporary
resident, and
(ii) return to Canada by the end of the period initially
authorized for their stay or any extension to
it
