On the part of Legend Box where it talks about "you can play only 1 Pokemon LEGEND in this way", is that just for the play of the card, or for the entire game?
It only lasts for as long as the Trainer is being used. It just means that if you reveal two or more complete Pokemon LEGENDs that you can only put one of them onto your bench for that trainer card played.
Source: PUI Rules Team (2010-09-23)