Do you need to be 18+ to sell a game made with unity3d?
If you are underage in your country you will propably have a limited contractual capability. To my knowledge Unity doesn’t enforce anything beyond that per se. Why don’t you just find a partner for your buisiness ventures, it’s a good idea to have an adult for doing buisiness, anyway. My parents would’ve supported that when I was that young, though there was no Unity and AppStores in that time…