This hoverboard doesn't have any unlockable upgrades.
Birthday is a hoverboard that was released with Subway Surfers World Tour: Copenhagen. It is the fifty-second limited hoverboard in Subway Surfers. Like any other hoverboard, it will protect you from crashing for 30 seconds. When crashed, the board will explode and recharge for a few seconds before it can be used again. It has the appearance of a birthday present. This is a free gift to celebrate Subway Surfers' 5th anniversary.