I have solved this problem guys, I have three saves for the collector trophy....... I have 2 completed files for Terra and Aqua (with all stickers), and a save where you only have to collect 1 sticker for Ventus...... First: delete the Birth By Sleep System Data (with the Mickey Emblem showing) Seco...

Does the Collector Trophy pop up if I get all the stickers (using the code) for Terra, Aqua, and Ven????
Does this work?