I have a deployed client site using a runtime at V 2.0 build 834
My Config tool Dev version is at 2.2 build 937
I have been exporting BSVs to the client site seemingly OK and have looked to see if there are any notes about when to upgrade the client runtime..
None in release notes that I can find.
The forward compatibility is not guaranteed, although will work in many cases. The safest option is to ensure the client has a build number that is the same or greater than the one used to export the configuration.