Unlock ALL horses!
This might be patched by the time you read it, but to 'unlock' all horses, do exactly this before it's patched and you can be any horse, even a pegasus!

Press play online/offline and change horse at the same time, if you pressed offline choose horse (if you want foals and rare press where the tab should be), then when you press the map you want (you dont have to be hero horse) rapidly press where the horses box should be. If you pressed online, press accept, then do the same as offline (select horse), after you do that, press a room and rapidly press ABOVE the middle of the box to avoid pressing create room. You should now be your dream horse! It actually works please let me know if your stuck and I'll help you, it took me abit to understand

Free hero horse
So click on horse quest. On the bottom left corner is settings. Click on settings. It should have music option and a thing for entering a code and a thing saying redeem hero horse or something like that. Click on redeem hero horse and boom your a hero!