There are several restrictions on replication definitions in mixed-version systems.
If you create or alter a replication definition that includes an identifier longer than 30 characters, only Replication Server 15.0 or later can subscribe to that replication definition.
After you upgrade a Replication Server to version 15.5 or later, you can only create, alter, or drop replication definitions if the site version is 1550 or later.
If you execute alter replication definition to drop some columns from the replication definition, and there is a subscription to the replication definition from a replicate site with a site version earlier than 1550, the primary Replication Server rejects the alter replication definition command.
Issuing any alter replication definition request with the with DSI_suspended parameter does not suspend any replicate DSI with site versions earlier than 1550.