Admission is granted for a period not exceeding three years, tied to the employment described, and extensions are possible. The application should be made once the start date, the duties and the duration are settled, because status obtained against an unsettled plan either fails or authorizes work the applicant will not be doing.
Apply to the schedule you can prove, not the one you hope for
Three questions should hold still before anything is presented: what the applicant will do first, when the work begins, and how long the engagement is now expected to run. Hypothetical example: Elise, a veterinarian whose American practice is still deciding whether she is an employee or a partner, cannot answer the first, which makes the ownership question a scheduling problem as well as a legal one. Two traps appear in the waiting period.
Beginning work remotely from Quebec for the American employer raises awkward questions about when the employment actually started and who was directing it. Travelling as a visitor and then performing productive work is a separate and more serious problem. Hypothetical example: a graphic designer at an agri-marketing studio is asked to start before a January trade show, and the studio proposes she attend as a visitor and simply help on the stand, which is exactly the improvisation that should not be made without advice.