While I have faced this issue a few times, especially with some UI elements when moving from 1 version to another, I found that the situation is much better in iOS (deprecated APIs are supported for a while before being removed) when compared to Android (of course, its my anecdotal experience and I'm not trying to generalise here) where some of the APIs were completely dropped or the behaviour was totally different between incremental versions. In our case we we had to implement the same feature in 2 different ways to support 4.0 and 4.1 Android versions.