In this video (https://www.youtube.com/watch?v=ZjPRj2Vp74U) Andrew mentions that Ionic builds different element design for each platform. Is it possible to prevent that, so the app looks the same on all platforms?
Yes this is 100% possible. This can be achieved with the Ionic $ionicConfigProvider. You can use this provider within your .config() method and do things like override which platform specific styles you want to.
Its a pretty powerful tool have a look at the docs for full info.