The Lv. 105 isn't a bug so much as an unintended consequence, since it appears Challenge Mode ignores the level barrier. But I wanted that Zekrom to have Bolt Strike, so it's 100 in Normal Mode or bust! The trainer rosters doc has Normal Mode levels unless otherwise stated.
Now understands, Drayano. But, (serious) how changes forme that legends? That's mean, you can't generate items to change forme or special move (like Meloetta with Relic Song)? Ok, I may don't answer, that's a simple question about changing formes.
And Zekrom's level 105... I think you love challenges.