No they aren’t. During the release period, they pretty much stop getting updates altogether.

The choice of programming language isn’t that important insomuch as Computer Science is not about coding.

Surely using Python to code OS course assignments does not make much sense. But that choice comes naturally with the course in question. Courses about a specific language are set out to become dated from the start.

Firefox used to follow semantic versioning of some sort, but dropped it in favour of just incrementing the major number.

It’s common. So does Chrome. And LLVM from the top of my head

Sid is not a rolling release. This is a common misconception.

In preparation for a new stable release, it goes through what is effectively a package freeze. Maintainers are discouraged from updating packages in Sid in order to focus on the new release. So almost no new updates are uploaded to the repositories until Stable is finally out.

That's not exactly a hard rule, just stuff maintainers do because it is far easier to still have normal flow of unstable -> testing for the freeze period, and keeping 2 ("actual unstable" + "unstable on the way to the new release") would be a big burden for maintainers.

Correct. This is why I said “effectively”. At the end of the day, Unstable does run behind during the freeze period. Same for Testing, obviously