This hoverboard doesn't have any unlockable upgrades.
Flying Horse is a hoverboard in / update. It is a limited hoverboard exclusive to the Collections feature. Like any other hoverboard, it protects you from crashing for 30 seconds. When crashed, the hoverboard will explode and need to recharge for a few seconds before using again. It can be unlocked by scoring 4.5k points in the Collections feature.
Appearance[]
Green Horse Statue Of Hoverboard
Trivia[]
The update added the Hoverboard in the files. In the board was added to the game in Collections but not for everyone because the Collections feature was not fully developed yet. Later in the update the function was improved and Flying Horse was released for everyone.