Complete the building 100% to select any floor.
Successfully complete Floor 13. In this mode, you can battle any previously defeated Boss again.
Note: This trick requires two deck recipes, naming one recipe A and the other recipe B. Go to the deck/bag screen. Load recipe B (touch the menu button above the "Ok" button, then the first button seen). Add the card you want to duplicate to the deck (max. 49 cards). Take out the card(s) (apart from what you just added) from the deck so that the number of cards is 50. Register the new formed deck recipe to deck recipe A (touch the menu button, then the second button seen). You will be prompted to overwrite the existing recipe; select "Yes". Load deck recipe B. You will now find the card you just added increases by the number you added. Note: Be careful not to register the new formed deck recipe to deck recipe B or you will lose a card instead of gaining one.