In addition, after the deployment of the ABM systems on the territory of South Korea, no rocket will not be able to pass undetected.
No air defense system is 100% effective. They may be able to detect the missiles, but there is no guarantee that all of them will be intercepted. Anyway I don't think that Kim will target Australia, when he is having Japan and South Korea nearby.
If the complex is one he can skip the missile, but if there are many then the chances are almost negligible. Miss one complex will bring down the other. The more that Kim no a large number of missiles. We do not yet know whether they will fly or not.