Is it ok to ask retrospective questions? By his I mean a problem or issue that someone may have had as a parent some time ago, that has been resolved and if so, how should this be done; do we state that it is a retrospective question?
It's absolutely fine to ask questions even when you already know the answer. In fact, it's even encouraged! Our help center says:
If you have a question that you already know the answer to, and you would like to document that knowledge in public so that others (including yourself) can find it later, it's perfectly okay to ask and answer your own question on a Stack Exchange site.
You don't even have to state that it's not actually a current problem of yours, because it doesn't matter -- chances are it is a current problem for someone out there, right now. And other site users will have been in a similar situation and they can add what worked for them, thereby further improving the options of future readers.
The same applies for "pretend" questions. I can ask a question where I pretend to have some problem that just occurred to me. It doesn't matter whether I actually have that problem or not, it only matters that it's a valid question that garners a few good answers.
Either way, this site becomes better because we get more good questions with more good answers. It's a win!