Is there a way (without hacking/powersaves) to use multiple Diancie codes on the same save file on my Pokemon Y? I tried using a 2nd Diancie code but it told me I already received the gift.
Hope this helps.
The codes are programmed to work just once for the trainer, the only way to get in two is by restarting your game.
Source: Have tried it myself, it always says: "You have already received this gift"
Hope I helped!