Your affairs going forward have nothing to do with your current application. If you decide to move south, you have all the rights to do so, even when your citizenship is granted.
This is a great answer. The application is all about you and yourself, nothing else matters.
It won't. Depends on how you take it. Some choose to go live and work elsewhere and that's fine. Just don't make it the focus point of the interview. Canada is expecting new citizens to add up to the society, culture, prosperity (i.e. taxes). And if you declare point blank that you are moving elsewhere upon receiving your Cship this might seed some wrong thoughts with the officials (passport of convenience). You are right in saying that there's absolutely nothing prohibiting one to leave the country though.
No, it is not an obligation to stay in Canada for citizens. BUT, before you become a citizen you remain a PR, you need to fulfill your residency obligation (2 out of 5 years). Leaving Canada after you submit the application gives officer the sense that you are getting a passport for convenience, instead of settling in Canada permanently. In some cases, that may trigger an RQ and extend the process unlimitedly. But these are all observations and guesses, no one knows for sure what impact it might have for doing so.
Residence Questionnaire. To evaluate if you have actually met the residence requirement. You can take a look here: https://drive.google.com/file/d/1Ha-f7FpFF06CzP4geBNX_GxhgbEGcTr5/view
Does this apply even if you have applied for citizenship, fulfilled the number of days and passed eligibility ?
Yes, it does. There are a few on this forum got this during/after interviews, even they had 1100 or 1200+ days, you can browse around the forum.
Whatever it seems you don't want to get one...
