Dynamo if first developed as the “Core” application. This is launchable as Dynamo Sandbox.Dynamo Core is then consumed by the applications which host it. The integrator will sect which version to work with, usually with significant effort around coordinating with other applications to keep things as consistent as possible.
However not all host applications update at the same pace - which I believe is what happened here, though I may be mistaken. If memory serves both Advance Steel and Revit all launches with 2.5, but Revit issued an update which integrated 2.6 while advance steel may not have. Meanwhile sandbox will keep producing new nodes.
To help ensure things work you will want to test all your nodes in the various builds. This can be difficult to set up but once done you should be able to quickly test via Dynamo Player if not even more automated (ie: journal automation in Revit). A possible shortcut would be to develop in the oldest build you want to use, and test in the latest version of Sandbox (so 2.5 and 2.11 here). If Sandbox still works it’s unlikely to have ever broken.