Answer
To restore backup of container(VE) made on 3.5.1 version to Parallels Virtuozzo Containers 4.0 it is necessary to do the following:1. Copy VE backup to default backup location of Parallels Virtuozzo Containers 4.0 node.
2. Run the following utility to synchronize old backup format with a new one:
vzbackupsync.exe After that this backup will be visible and available for restoration.
3. Restore container backup.