As much as possible, the development team at Mi-Co strives to maintain compatibility between versions. In general, previous Client and Designer versions are compatible with updated Server versions.
Mi-Forms Designer
In the Designer, older ".mfd" files (Mi-Forms Designer Files) can be opened by newer Designers however once the file is opened and saved, the new format will be incompatible with previous Designer versions.
Mi-Forms Server
In the Server, once a Server is upgraded, previous customer databases must be updated to the newer version. When the database is updated, the Server executes a series of scripts to update it to the latest. ( Mi-Co Support highly recommends backing up critical databases before updating a Server and/or updating the database. ) Please refer to the Mi-Forms Server Documentation, "Installation", "Upgrade from Version x" for more detailed information.
Mi-Forms Windows Client
In the Windows Client, most older ".mft" files (Mi-Forms Form Template files) may be used with newer clients with very few exceptions. Updating form templates based on an updated Designer will ensure that the latest features are available however. While communicating with the Mi-Forms Server, an older Client should not have any issues however Mi-Co recommends upgrading Clients to at least the same "major" version as the Server (e.g. Mi-Forms Client 9.1 with Mi-Forms Server 9.5).
Mi-Forms for iOS and Android Clients
The iOS and Android Clients should be updated regularly to be compatible with the latest Server version. If a new version of the Client is published to the app stores (Apple iTunes App Store or Google Play store), do not install latest without certainty that the versions are compatible. Minor versions are compatible (e.g version 9.5.4 Client and version 9.5.1 Server). In particular, the differences between Version 9.1 and Version 9.5 were substantial. Major versions may have some compatibility issues - please contact Mi-Co Support if considering an update.
Before updating a Server or deploying new Clients, it is highly recommended to test these scenarios in a dedicated test environment that mirrors the actual production environment.