How does C not violate rule 3?

Rule 3 states that on Saturday either G or H can be shown but not both. This means that if G is shown, H cannot be shown and if H is shown, G cannot be shown. Rule 3 further states that no film can be shown AFTER either G or H has been shown. This leaves room to show a film BEFORE either G or H is shown. That film now being the only remaining film, L. In option C, On Saturday, L is shown, then G. So rule 3 hasn't been violated. I hope this explanation helps you.