1. See QuickStyle Sets
2. Style sets only include styles that are set to display in the Quick Styles Gallery.
3. They include all styles that are set to display in the Quick Styles Gallery. This may include styles you do not want.
4. Styles can be based on other styles, which may or may not be included in the style set. I.e., based on normal.
5. Numbering should be attached to styles following directions at How to create numbered headings or outline numbering in Ribbon Versions of Word by Shauna Kelly
6. I do not know that the list styles get attached to quick style sets.
7. I have used macros to transfer them and that has worked.
   A Global StyleSheet in Microsoft Word?
   Outline Heading Styles Global Stylesheet