my camera Canon G9x Mark II goes to f/2, however on Av mode outdoors, it did not allow me to do so. why?
What does it do at that Av setting indoors? Shade? Reduced lighting?
My questions are based on the idea that, under your stated conditions (outdoors assuming bright daylight), the camera may not be able to adjust shutter and/or ISO sufficiently to give you a proper exposure. You know — protect you from yourself.
If the camera allows f/2 indoors/shade/etc, then that's possibly what's going on.
The most likely reason is that even using the camera's lowest ISO available and the camera's shortest exposure time (a/k/a the "fastest" shutter speed) available, the conditions under which you are shooting are too bright to get a proper exposure using f/2. So the camera limits you to the widest aperture that will allow good exposure for the light in which you are shooting using the shortest exposure time and lowest ISO of which the camera is capable.
The lens on your camera does not have a fixed aperture. This means that if you are zoomed in at all, your widest aperture available will not necessarily be the same as when you are zoomed to the widest your camera can go. It is possible to construct lenses that have fixed (widest) apertures, but these are more complex, more expensive and heavier than variable aperture lenses, and hence are not ideal for compact cameras.