>So what I need to know is: will Prod on 5.1.3 fail to do any composer operations in DR vcenter when DR Composer is 5.2?
>Conversely, will DR 5.2 fail to do any composer operations in Prod vcenter when Prod Composer is 3.0 (not upgraded yet)?
Yes on both counts, they need to match up so you'll have to set up additional stand-alone composer server instances or upgrade everything at once as you won't be able to share them across mixed versions of View connection servers.