no, no, that;s different. with SIN card doen't mean it's working permit. if u read the stuff from CIC carefully, u would see that on campus working is an exception from other kind of working permitt, actually u don't need any working permit from HRDC in order to work on campus, that;s why international students can apply for working on campus. you SIN is differ from PR's SIN, the number start differently. If u obtained working permit from HRDC, that means u are registered emply at HRDC, u gonna pay all the taxes, EI, pension etc.
毕业后means the latest degree u have obtained.