This hoverboard doesn't have any unlockable upgrades.
Kitty is the sixth limited hoverboard in Subway Surfers. 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.
The board has a picture of the Japanese flag and a trademark cat design on it.
The Kitty board was introduced in Subway Surfers World Tour: Tokyo. It was never released professionally as a limited hoverboard to purchase with in-game coins or while collecting tokens. Strangely, for some Subway Surfers players, while buying the Fortune board, it somehow changed into the Kitty board instead of what was intended. It was most likely a bug.
It's possible that the trademark cat design on the board is a Lucky Cat, a very popular item in Asia that is said to give you good luck.