$A$ virtual image cannot be focused on a screen. Yet when we see a virtual image,we obviously bring it to the screen that is the retina of our eyes. Is this a contradiction?

(N/A) No,this is not a contradiction. The lens of the eye converges the divergent beam of light (which appears to come from the virtual image) onto the retina. This process forms a real image of the virtual object on the retina,allowing us to perceive it.