As of August 3 2015, Kitkat version of Android operating system was still the leader operating system on Android based devices with almost 40%. The second is Jelly Bean with about 33% usage over 3 versions of Android: 4.1, 4.2 and 4.3 ( all called Jelly Bean ). Surprisingly the latest version, Lollipop, launched almost 1 year ago, with only 18% from 2 versions: 5.0 and 5.1 .
This is one of the biggest problems for Android ecosystem: the fragmentation of OS versions. This might be a pain for developers because they have to make sure that their app is compatible with all versions. While there is no problem for old apps, because when a new version of Android is released, backward compatibility for apps is provided, but if someone wants to use the new features of the API available only in Android 5.0, they might want to also provide alternatives for older versions ( more than 80% of android phones worldwide ).
The most affected of this problem are developers, but normal users with older version also suffer because they find our about a new app, a great app, but they can’t get it because it is not compatible with their version. Unless you buy a Nexus or a high-end smartphone every 1-2 years then it is impossible to keep up and fully benefit of every android app. Most phone developers only provide 1 or 2 updates.
However, the most popular apps are working usually for all versions of Android. This is also the case for Casino apps. Here is a list of Casinos that offer Apps for Android . Android apps provided by 32Red, Leovegas or Betfair are working on most Android versions except Froyo and Ecalair, versions who accounts for as low as 0.30% of total Android users.
There is a consistent effort put by application developers to assure that the product follows the latest standards and keep up with the latest features provided by new versions of Android, but in the same time to make sure that it works for old versions too. There are over 20 different versions of Android versions, despite the fact that some versions received the same name. Probably this is the reason that popular apps are bigger and bigger in size. Not only because they are more advanced as they used, but they have to contain compatible code with different versions.