Enter the beta access code: CrusaderKings (this may be required by Paradox to see older versions).
Disable and select version 3.0.1.1 from the list. Key Content in v3.0.1.1 Download Crusader Kings II v3.0.1.1 Online
Select 3.0.1.1 - Old version 3.0.1.1 from the dropdown menu. Steam will automatically download the legacy files. : Open the GOG Galaxy client. Go to the game page and select Settings (next to Play). Choose Manage installation > Configure . Enter the beta access code: CrusaderKings (this may
