It is not possible to perform online migration from the node installed with Parallels Containers version 4.7 to the node installed with earlier versions because the migration procedure in the version 4.7 relies on the functionality which is not available in elder versions.
Also, online migration within the same Virtuozzo version is limited by the rule: migration is possible from an older kernel to a newer one. Migrations to the servers with older kernels might fail due to different format of the memory dump file or due to missing features in the older kernel (like support of some guest OS in a container).
For more information see this article:
113024 Containers online migration product versions compatibility.