Avamar Update/Migration

Hello All, looking for some input from anyone that can help give me some answers to some questions..

We have an Avamar 7.3.0 on site, with vCenter 5.5, we are looking to update vCenter to at least 6.0 with latest update, we'd like to go higher but we know avamar is a problem for this.

What is the highest vCenter 6.0 release we can run with 7.3.0, I know there is a compatibility site, but it isn't loading for me and I get an error that the page can't be reached. So I'm hoping someone here are ran across that information.

We are also looking to update to Dell IDPA (which from what we have been told basically runs Avamar on the back-end). Has anyone heard or seen evidence or documentation that the backups in the older Avamar can be migrated to IDPA?