Challenge to be a Unicorn

All unicorn's have to undertake a challenge before they get their golden horns, and it's not an easy task to undertake, first, on earth they have to spend a time being a true living horse, they can be either someone's pet, or a Police horse or a free and wild horse, or a working horse and of any breed or have any colour coat. To become a Unicorn they have to earn golden stars.