Q: Is it possible to set a secondary preferred language on the iPhone?
Background:
On the Mac Desktop it is possible to select a "Language Preference" order, so that if your favorite application isn't localized for your primary language, then it will prefer the second best (Good example here would be a German user who speaks fluent french, but not English trying to use an application that has been localized for English and French should be able to specify they prefer the French to English):
However in iOS it seems that it isn't possible to specify a secondary (or 3rd preference), only to choose what your primary language is, at which point, iOS then makes English your second preferred language. (So in our first example iOS will incorrectly show you the English version even if you'd have preferred the french, unless you restart your springboard and change languages every time you want to use the app):
I'm not concerned here with the keyboard internationalization, but just with viewing the applications in the correct format.
Best Answer
As of at least iOS 8 you can change the order of languages in Settings > General > Language and Region under the heading Preferred Language Order.