Mega evolution pokemon moon question

[Blondie987]

hey yall i have a question regarding pokemon moon and mega evolution.  i've used pkhex added in the correct held item for mega evolution added in the mega ring but when i click on mega evolution in game no mega evolution or transformation of pokemon occurs the button for mega evolution in game just lets off a chime of sorts and nothing more.  is a special flagged needed to trigger mega evolution in game or have i done everything correctly?

[Kaphotics]

Beat the game first to unlock the feature.

[ArtemisAbsol]

Is there any way to unlock or edit the particular Key Item--the Key Stone, if memory serves--into your inventory before beating the game?  I saw the ability to set a few flags via PKHex, such as the Champion flag, but no way to add in Key Items.