Could you transfer wormhole legendaries in Pokemon USUM that are shiny to games where they are shiny locked and the Pokemon still be shiny?
To my knowledge, all Pokemon have shiny sprites coded even if they're shiny locked (to prevent the game from crashing if they're hacked in). Shiny locking only applies as far as the encounter and can't affect the actual data for the Pokemon, so transferring it back wouldn't delete the shininess or damage the game.
You can not transfer any Pokemon from gen 7 to x, y, omega ruby and alpha sapphire although pkhex allows you to get shiny locked legendary its not really a great source cause its cheating