If you go to the Pokemon Challenge menu, press "Delete" on one of the quizzes (your choice on which one), then enter PHSKUTDF, you'll unlock a quiz that, upon completion, will unlock the Pokedex data for Genesect.
In the Quiz Numbers 37-39, you can enter a Keyword to enable various quizzes. Certain Keywords will unlock additional features; complete the quiz to access the reward.
Delete one of the quiz codes from #37 onward (it doesn't matter which) and enter the following code. Once you complete the challenge quiz created by the code, Meloetta's data will become available.
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