Go to Beta Quest world 2 and go to the entrance to the market(In this world, the hyrule bridge is down). Then inside you will find a potion shop! The lady will tell you about the door to your left. Go through it and you will find yourself in the windmill in kakariko village!(That's strange, she said there was another potion shop) Talk to the dude with the music box, and he will teach you the song of storms, as soon as he does, everything will be enabled, as if you are playing the real game with every single item for as long as you want! However, if you save, it doesn't do anything. Now you can beta test every item.