The copy that Exterminator Magmarch's ability creates is created on the stack, so it's not "cast." Other abilities that trigger when a player casts a spell won't trigger
The user interface clearly shows you which phase youre in at any given moment, and highlights the cards in your hand and on the table that are eligible to be played at any given moment
5 Metal Energy: Sun & Moon Base Set (163/149) - $12.94 The Final Slot, The Ultimate Shine
The 2 cards I got in them (Raquaza lvl X, and Charizard lvl X, respectively) were inspected by me and seemed to be real
Characters cannot attack on the turn they are played, or on each players first turn
If the spell that's copied has damage divided as it was cast, the division can't be changed (although the targets receiving that damage still can)