Are there missile variants 5V55KD and 5V55RD?
I'm not sure. On a Hungarian forum I saw a long post with many missile varaints which are not mentoned elswhere and their capabilites were incoherent.
5V55KD - 75 km range. The guy said this was still pure RCG, but this seems to me impossible or inaccurate. Never was a SAM system with pure RC guidance with higher than 55 km range because it is simply too inaccurate the guidance without using nuclear warhead. This is why got nuclear warhead the Nike Hercules and even the ARH guided BOMARC.
5V55RUD - 92 km range. Also you cannot find lots of sources about this to verify this. If you check the document the eng. range diagram of S-400 does not show this range with older missiles and I have never seen any diagram with such range. only 47, 75, 150, 200 and 250 km range diagrams are available with 5V55K, 5V55R, 48N6, 48N6D, 48N6DM missiles. Maybe were very small and limited qty. other types but main missile variants are these.