Here is how The Challenge begins, Cheating to win and Yuna's back goes in The Journey Back to Life Part 2.
Meanwhile, Titanic, Britannic, Olympic and Titanic II were about to begin the ceremony.
Titanic: Are you girls ready?
Emerald: What's gonna happen now, Mom?
Rarity: We'll see, Emerald. We will see.
Meanwhile, the challenge had begun.
Xibalba: For your challenge, You must go on top of a tall mountain without using your wings or magic.
Princess Yuna: Well, here goes nothing.
The Candle Maker: Ready!....Set!.....Go!
As Yuna was halfway on top.
Princess Yuna: Guess there's no choice. (uses her magic)
Xibalba: Using magic to reach the top, Are we?
Princess Yuna: Sorry, I didn't mean to. It's just that I want to go home badly.
Xibalba: Don't take it to hard on yourself. I know exactly how you feel.
Princess Yuna: Really, Xibalba?
Xibalba: Yes, I cheated too. Because I wanted to win the wager and rule the Land of the Remembered really bad. It happens.
Princess Yuna: No hard feelings, La Muerte?
La Muerte: No, Of course not. And because you saved your sister's life, We're going to restore yours.
The Candle Maker: Besides, You're writing your own story on The Book of Life just like Manolo Sanchez did.
Princess Yuna: (determined) Xibalba, La Muerte, Candle Maker, Take me home.
Xibalba: Very well, Princess Yuna.
The Candle Maker: With accordance of the ancient rule!
La Muetre, the Candle Maker and Xibalba: We give you life!
So, Xibalba, La Muetre and the Candle Maker restoring Yuna's life.