From my understanding, until you have received some sort of confirmation letter from your school saying you have met all the requirements or have attended your graduation ceremony, you haven't completed your studies. This means that you are still a student and if your study permit and off campus work permit are valid then you should be able to work (even full time cause its usually break period after finals). Just because you have completed your finals or have also received your grades back doesn't mean you have completed your studies (school needs to verify you have met all the requirements and give you a confirmation that you have). And you can only apply for PGWP after getting the confirmation from school that you have completed your studies.