MSB was launched on the heels of the first iРhone in 2007. Versions 1.x-5.7 Support their listed iOS versions and all prior versions.
MSB versions 6 and up have a rewritten engine and interface and support the latest version at time of release and select prior versions. The release notes state which versions the release supports.
Pro licenses enable the ‘legacy’ engine and can view all versions, but development on this engine has been discontinued and support for any issues is limited.