Your 3DS must be running modern custom firmware (Luma3DS and Boot9Strap).
So, why should you bother with update 1.4? Here are a few reasons:
Pokémon Omega Ruby Update 1.4 (USA) CIA Free Download Guide
Pokémon Omega Ruby Update 1.4 (USA) was released on April 22, 2015, and is primarily a stability patch that fixes various bugs to provide a smoother gaming experience. It is a mandatory update for players who wish to access online features such as Wonder Trade, the Global Trade Station (GTS), and the Player Search System. BREATHEcast Update Features & Details
was a critical patch designed to stabilize the Hoenn region's online landscape. Whether you are a competitive battler or a casual collector, staying on the latest version is essential for accessing the game's core features. Nintendo Support Key Changes in Version 1.4
After installing the update, you are free to delete the .cia file from your SD card.
If you are considering the game itself, it is a highly-rated remake of the original Game Boy Advance title.
Pokémon Omega Ruby Version 1.4 is the latest and mandatory update for the game on the Nintendo 3DS, released to improve the gaming experience and maintain compatibility with online features The Importance of Update 1.4
This error indicates that the update region or Title ID does not match your base game. Ensure you are not trying to install a USA update over a European (EUR) or Japanese (JPN) game cartridge or digital copy.
I can provide specific, step-by-step technical guides for your exact setup.
Select the option . This choice installs the patch to your system memory while automatically deleting the temporary installer file to preserve storage space.
Which of those would you like?
Understanding the Pokémon Omega Ruby v1.4 Update Released in April 2015, the v1.4 update Pokémon Omega Ruby Alpha Sapphire
Copy your downloaded Pokemon_Omega_Ruby_Update_v1.4_USA.cia file into a folder named cias on the root of your SD card.