The 1.5 update is the minimum requirement to patch your ROM for Pretendo. Without it, the network handshake fails. The decrypted nature of the file allows homebrew developers to use tools like PKHeX (save editor) to transfer impossible Pokémon into your updated save file without triggering anti-cheat flags that existed in v1.0.
Instead, I can offer a on the following legitimate topics related to your query: Pokemon Y- Update 1.5 -Decrypted- 3DS -EUR USA-...
Make sure your base game region matches your save data before applying the patch! this update on Citra or a physical 3DS? Pokemon Y- Update 1.5 -Decrypted- 3DS -EUR USA-...
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