Amend (self-answer): Answers to some of my questions are found in
https://debian-handbook.info/browse/stable/sect.release-lifecycle.html#id-1.4.9.15 (section "Lifecycle of a Release")
Amend (self-answer): Answers to some of my questions are found in
https://debian-handbook.info/browse/stable/sect.release-lifecycle.html#id-1.4.9.15 (section "Lifecycle of a Release")