Retake with additional questions

I would like to create a survey where users can answer questions, return to amend their saved responses and have the capability to add/edit additional questions to that same survey/question. Users would not need to retake their initial responses - those answers would be saved and users would see additional questions within the survey or additions to a particulate question. Note this survey would be embedded within a Learning Management System such as Canvas or Articulate. Users would be added to a contact list and authenticated, the anonymous link would be embedded within the LMS making for a seamless transition to Qualtrics. The quiz contains confidential information so emailing a retake link is out of the question. I am stuck on the adding/editing questions yet still retaining original responses. Any and all assistance in finding a solution to this would be appreciated.