When you grow up, and before talking for the second time to Sheik on the Time Temple to learn the Prelude of light, she will tell you that in your home you can rest to revive past battles. That means you have unlocked Boss challenge to fight each boss in the game (after you had beat them in the story) in your house. To unlock the last challenge (all bosses one after another) you have to beat them all in the challenge mode.