When you beat Vaati's Palace for the first time you unlock the Realm of Memories, Level 1 is Link to the Past consisting of Hyrule Castle (exterior), Hyrule Castle (interior), and the Lost Woods. I was hoping for a Dark World stage. Bummer.
Level 2 takes place in Link's Awakening. Stage 1 Takes place in Northern Mysterious Woods, The Swamp, and near the Hag's hut. Stage two takes place in the Tail Cave, some rooms have been omitted though (namely the first Key room and the Roc's Feather Room). The final stage takes place in the Tal Tal Hights area, some tricky jumps are assured.
Level 3 TOTAL NOSTALGIA TRIP HERE! It takes place in The lower overworld in stage 1, EAGLE DUNGEON in stage 2, and Graveyard/death mountain in Stage 3
When you have collected a total of 30,000 or greater you will unlock the Hero's Trial. I can't go into detail as I have only managed to BARELY beat Level 1. Warning! Darknuts are at the final stage right before you finish the level and you must kill all 5~10 of them! It took me an HOUR to finish it because of how balls hard the foes are as well for the mind-boggling puzzles!