This glitch allows you to use Farore's Wind anywhere. You cannot have won Epona off Ingo yet.
You can now use Farore's Wind anywhere. However, all C-items are disabled except for the Ocarina, and songs played on it won't do anything. Performing some actions, such as swimming or climbing a ladder, will disable the B button. To return the game state to normal simply return to Lon-Lon Ranch during the day.
This glitch allows you to put bombchus and the fairy slingshot on B as a child.
Once the game ends you'll have the Slingshot/Bombchus on B. If you bring up the subscreens (pause) the B button will return to its normal state (Kokiri Sword).