Does Apple only store 2 digit version numbers? I am developing Xamarin.Forms application to run on iOS. 

I want to check the version number of the user's current app against the latest version in the app store to prompt for an update. The version number that I have saved in my info.plist file is "x.x.x" with 3 digits, however when I am in code and returning lots of information about my application, the version number is returned as "x.x" with only 2 digits, even though in config files it is specified as having 3 digits. 

Does Apple only provide 2 digit version numbers and I need to check against this, or is it possible to retreive 3 digit numbers too?
This would appear to be a problem with your app's code. Apple uses three part version numbers everywhere, from first-party apps to the OS version number itself. Check if the version number is reported correctly when using Get Info from Finder on the app bundle.