Questions/ Questionnaire Templates/ Questionnaires

Summary:

While the steps to be followed regarding the creation of questionnaires are quite simple and intuitive and there are also plenty of resources on this community, I do have some topics that are not that clear, therefore, I need the help of the Community.

Content (required):

1. What is the difference between Questionnaire Templates and Questionnaires?
2. If there is a need to modify the questionnaire (by adding/ removing questions, by adjusting some questions), which task has to be used: Questionnaire Templates or Questionnaires?
3. If the questions/ questionnaire templates/ questionnaires are created with an Owner and the Privacy is set to Public, can anyone with the right permission modify them later? Or is there a way to create these without an Owner?