This game, as well as its subsequent re-releases on PlayStation Vita, iOS, and Android was never released outside of Japan. See this FAQ post from the Réalta Nua English Patch tumblr for content differences. This version also has the adult content from the original game removed, altering some of the game's story scenes to reflect these changes, however, it also features the new content that was previously exclusive to the PlayStation 2 version prior to this PC port. The PC version of Fate/stay night is based on the PlayStation 2 port, and unlike the original Fate/stay night, the three routes in the PC version of Réalta Nua are divided between three separate episodes with their own executables, starting with the Fate route released on Decemthrough .jp.
It is an updated version of Fate/stay night. Fate/stay night is a visual novel developed by Type-Moon.