What is the ruling on wiping over a thigh-high compression stocking that has an opening at the bottom, and should one wipe over its entirety or only up to the ankles?

It is permissible to wipe over "compression socks" if they cover the obligatory area (the feet up to the ankles). One should wipe over the part of them that must be washed during ablution, and it is not prescribed to wipe over anything beyond that. A slight opening at the bottom of the sock does not prevent wiping. Wiping becomes invalid if the sock is removed, and it should only be worn after ablution is complete.