Arthur, there are two versions of DCS available. The 'stable' version is currently 2.5.4.27430, which was the previous Beta version number. The current Beta number is 2.5.4.28090. Version number is displayed on the main screen in the lower right corner. If you run both, you'll need two totally separate installs of DCS on your machine, and two execute files, of course. I have both installed on my storage drive, one under 'E\DCS World' (the Beta) and one under 'E\DCS 2.5 STABLE' (the stable version). Both have their own individual .exe files inside their separate game folders.
The beta is the "development" version, implementing new things for testing by the community to look for faults. It's also a nice way to get a head start on new features, but most of us, including myself, run the stable version almost exclusively.
Here's the link to the download page. Note the three different versions. 2.5 Stable. 2.5 Beta. 1.5 ("Legacy"). The top one, 2.5 Stable, is the one being currently run on the Dogz server.
https://www.digitalcombatsimulator.com/en/downloads/world/