There's no Question API to navigate through a survey; not really what those are designed to do anyways. Branching logic in the Survey Flow is also a clunky solution for showing a temporary question as it presents its own set of problems.
What if you added the Help button to the question title body and then added hover text (essentially a tooltip) with the additional info you want to display to users? Link to CSS documentation. This way, you can add on-demand, additional instructions without navigating away from the page. You can also style this pop-up hover box to look however you like (see that CSS link for an example). I've used this hover text solution on statements in a matrix table to provide context to user about mathematical metrics we were calculating for them. It's a really elegant solution and a nice trick to keep in your back pocket.