Thank you so much for your prompt reaction and the useful information. Do you have an idea of how much will cost me huring the service of a Lawer for such type of case. And for my application there is nothing particular except the request that the request was actually the CIT 0171. And that I really did went out of the country sevral time. But ensure that I really fullfilled the necessary physical presence.Note: the post you quote was made more than a year ago. Older posts can be helpful but things change and can otherwise be dated or in need of updating. I am no expert and am always trying to learn more and understand things better, and am well aware that what I stated a year ago may need some clarification or correction.
One of the things we have learned since that post is that after the surge of new applications in late 2017 and early 2018 there has actually been a significant decline in the number of new applications. Hard to figure out how this has affected processing timelines.
Your timeline is remarkably long. I could only guess at what might be the problem. If the request for supplementary documents was the CIT 0171 form, which is the Residence Questionnaire and sometimes referred to as the full-blown version (in contrast to CIT 0520 often referred to as RQ-lite), your application could be in a lengthy queue waiting for a Citizenship Officer to prepare a referral to a Citizenship Judge.
Some here will recommend making the ATIP request for a copy of your file. Enough time has passed to justify doing that. However, I am not sure you will learn much from what you get.
In any event, YES, you can request that IRCC take action on your application. Whether that will lead to action is difficult to forecast. Such a demand is a prerequisite to pursuing legal recourse (via an application to the Federal Court for Mandamus). It is best to consult with a lawyer first, and if this is the route you go, to have a lawyer make the demand and otherwise prepare to make a Mandamus case.
BUT what you should do depends in significant part on what the issues are. You know your case, your facts, so you should have a fair idea why there are questions.