This difficulty level remained in the game files, but was blocked by the developers. The Prince's health is at Normal levels, and enemies will need about 17% more hits than Hard. In my opinion, it is a little easier to play than on Hard. I almost got around to taking the mask without any problems.

To install, replace the file PoP5MAINMenu.mgm from the archive in the following path: "Path to game/Menu". Make a backup copy of the file before replacing. To start, start a new game and select Impossible.

Tested on an English license; the Russian license will most likely have problems with fonts. But you can start a new game, save and restore the file back.