4D provides two releases of a version of 4D simultaneously.

The typical version is now called the Long Term Support (LTS) releases. This is also refered to as the ".x" versions where x is the intermediate number. For example, 19.0, 19.1, and 19.5 are all LTS releases. Each never release, including nightly builds and hotfixes, in the 19.x will typically only contain bug fixes unless a critical issue needs to be resolved.

There is also the now called Feature releases. These are also called the R-releases termed by the versioning label of ".Rx". For example, 19R2, 19R3, and 19R5 are all Feature releases. The R-releases start with R2 and are typically available immediately after the .0 release of the LTS is available. The versions of the Feature releases are not related to the LTS releases. Such as 19R2 is not the same or newer than 19.2, it is actually older. Feature releases are dedicated to providing developers early access to features from the next LTS version. Each 19Rx version will contain new features that are intended for 4Dv20.x and as such, the entire Feature release is no longer supported when the next LTS is released.

Since the main versions of the LTS and Feature releases are the same, it can be possible to open a database and datafile and move back and forth between a LTS and Feature release of the same version. However, the information above should be kept in mind. If a new feature is ultilized when developing in a Feature release that is not in the LTS release, the command will not exist when opening the database back in an LTS release, even if the LTS release is newer than the Feature release.
As such, it can be better to keep two versions of a database, or keep track of code using new features and disable them whe moving from a Feature release to an LTS release.

See Also:
https://us.4d.com/product-release-life-cycle