I thought about creating a "question" in order to remind (or "honour") all the old Ubuntu releases (4.10 Warthy - 16.10 Yakkety).
But this question is mostly like a discussion one, not an answerable one.
The asking help on the right side says that I can only ask questions which can be answered.
Can I ask this kind of question?
If what you are contemplating posting is not an actual question at all, then it's unlikely that it would be reasonable to "ask" it on Ask Ubuntu. At least not on the main site. There's considerable leeway about this here on meta, but only in the sense that not everything has to be a question. Scope still applies here, so I expect we would close a "list of Ubuntu releases" question here, on the grounds that it's not about this site.
Therefore, from your description, it sounds like the post you're interested in creating might be suitable neither on main nor on meta. But your description is vague, so it's hard for me to be sure.
If you have an actual question, and the question can be answered based more on facts and experience than on opinion, then your question will probably not be closed as "primarily opinion-based." Unlike here on meta, on the main site questions are expected to be answerable, at least in principle, even though occasionally a question is hard to answer.
Questions about Ubuntu history are on-topic. This includes questions about what distros have existed, what they were called, when they were released, and--so long as it's a specific question--what features they introduced. I am reasonably sure--and certainly hope--that it also includes questions about official Ubuntu resources related to them, such as where official old documentation may be read and where old ISO images may still be downloaded.
However, questions about specific problems or tasks using end-of-life releases--that is, where the release became unsupported before the question was asked--are off-topic. The exception is if it is asking how to upgrade to a supported release. In the help, the last item listed under Questions that you should avoid is:
Support for versions for Ubuntu releases past their Support or "End of Life" (EOL) — unless the question is asking how to upgrade to a supported release.
If you're contemplating asking and answering a What are all the Ubuntu releases? question, that's on-topic and I see nothing wrong with it, except that you should search hard first, because I suspect we already have one. It might also be considered a duplicate of Where can I find the status of the released versions of Ubuntu?
Also, while I think there's nothing wrong with such a question, it will never replace https://wiki.ubuntu.com/Releases as the go-to source of information for all releases ever, their current status, when and how they were supported, and their release notes.
Finally, one correction: you say that the "old releases" are 4.10 Warthy - 16.10 Yakkety. Usually the phrase "old releases" is used to mean "end-of-life releases." If that's what you mean, you should know that Ubuntu 16.04 LTS Xenial Xerus and even Ubuntu 14.04 LTS Trusty Tahr are still supported today. 16.04 is even the current LTS release; many, if not most Ubuntu users, run that. (If instead by "old releases" you mean "all but the latest," then that would include Ubuntu 17.04, since Ubuntu 17.10 is out.)
