afaik the versions need to be the same, like mentioned here: Distributed monitoring - Scaling and distributing Checkmk
The Checkmk-version (e.g. 2.0.0) of the remote and the central site is the same — mixed versions are not supported. The patch level (e.g. p11) may be different in the most cases. But in rare cases there will be an incompatibility even here. You are then obligated to stick to the exact version (e.g. 2.0.0p11) on all sites to allow both sites to work with each other without any problems. Please notice because of that always the incompatible changes at each patch version in the Werk list.