Is it possible for D. Meloetta to use R. Song?

I have no idea if it can learn Relic Song and it is the only way for it to change into its Magician form (which I honestly like better)

D. Meloetta can learn Relic Song and it does change it form once the move is used in battle.

Where/when though?

Delta Meloetta learns relic song by a move tutor in the Alpha Temple of No Man`s Land, before that you must have defeated Reukra in the Throne of Hegemon.