No, a survey QR code does not change when updating and republishing the survey in ArcGIS Survey123. When publishing a survey from either Survey123 Connect or the Survey123 web designer, the survey can be shared through a QR code, which can be accessed from the ArcGIS Survey123 website. Refer to ArcGIS Survey123: Link to a survey for more information. The same QR code can be used to open the updated and republished survey.
However, creating a copy of an existing survey and publishing it creates a new QR code for the new survey. Refer to ArcGIS Survey123: Copy or delete a survey for more information on copying an existing survey.