Is there anyway possible to implement challenges and achievements in an app without using Game Center. The current app that I'm working on is not a game, but has challenges and achievements based on photo users submit. For example if a user uploads a photo of their pet, they get 50 points for submitting that picture.
You can use that, I create a simple class for iOS game center in GitHub https://github.com/DaRkD0G/Easy-Game-Center-Swift