Koomazaz: The GOG version of Arkham Knight does NOT have Denuvo.

The Earth-2 Batman skin IS INCLUDED and unlocked, without needing a mod. Same as Epic.

The game does not have the ability to log into WBPlay, so the Anime (Gotham Knight) and Zur-en-Arrh skins are NOT available via official methods.

The textures and models for the Anime and Zur-en-Arrh skins are still included in the game files, so they can be unlocked via a mod.

The PS4 Exclusive DLC (Justice League 3000, Classic TV Series/Adam West skin, Classic TV Batmobile skin, and Scarecrow Nightmare missions) are still missing, as expected.

The Classic TV Series Batman skin can be modded in, as with the Steam and Epic versions.

There is currently no way to unlock or mod the Justice League 3000 skin or Scarecrow Nightmare missions.

In total, there are 19 Batman skins included without modding, and three of them (Batsuit 8.03, 8.04, and 8.05) are unlocked via gameplay.

Kyousuke.: May I ask what kind of mod is needed to unlock the anime, zur-en-arrh skins, as steam received an update just yesterday that automatically unlocked them, which means that we are SOL for those two outfits...

TheMonkofDestiny: https://www.gog.com/forum/batman_arkham_series/about_the_dlccostumesperformance_in_arkham_series_on_pc/post6

I would wait to see if GOG gets the update that adds in the two costumes. I can't realistically see why it wouldn't, it just has to go through a middleman process before the update is pushed to the people who bought it here.