When you boot a EUR ROM, the game asks you to select a language. Choose . A proper v1.4 ROM will have the full Spanish script, including:
Example verdict (assumptions based on typical community patches) pokemon omega ruby update 1.4 rom espa%C3%B1ol
Once installed, the version number will appear on the game's title screen. For Citra / Emulators When you boot a EUR ROM, the game
For legal reasons: