Due to the way the frontend and backend of Flex5 work, the engineering team have setup a requirement that the release version of the app running on devices must match the release version running on the server.
To clarify, Flex breaks public release versions into three parts: The main app version, the release version, and the patch version. For example, 4.25.0 represents Flex4, release 25, and no patch.
During our initial release phase of Flex5, it's main version is 0, so you'll often see things like 0.25.1 or 0.26.0. Eventually, this will probably change to something like 5.30.0.
The important factor in determining compatibility is the release version. In other words, the middle number of the version must match for the Flex5 apps to interact with the Flex5 backend.
In the rare case where the new app releases to the app stores ahead of our backend update, devices set to auto-update may experience a temporary interruption of services until the backend updates to the same release version.