Copying GX attacks

[Magic_Umbreon]

If I use Evolutions Clefairy's Metrenome attack, does that count as my GX attack for the game?
What if I have already used a GX attack, can I still declare Metrenome?

 

[PokePop]

You might want to check the Compendium rulings that were just published:
http://pokegym.net/forums/showthread.php?187799-Compendium-Updates-for-January-5th-2017