HVAR can replicate referential constraints specified in replication definitions only if the outbound route version is later than 15.5.
HVAR works if the outbound route version is earlier than 15.5. However, no referential constraint information is available to a Replication Server with version 15.5 or later.
Continuous replication is the default replication mode available to all supported versions of Replication Server. HVAR is only available with Replication Server 15.5 and later.