VMware Compatibility

VMware compatibility mentioned in Platform Notes for most recent versions of vSphere. Is there any backward compatibility? As an example, OpenNebula 6.6.0 supporting vSphere 7 according to the Platform Notes.
Another question, is there any way to download vOneCloud older versions? Because there are some strange issues about VMRC, SSH and vCenter customization on OpenNebula 6.6 with vCenter 6.5 and ESXi 5.5 and 6.5.

Seems, there is no backward compatibility and because each version tested on the versions which have motioned in Platform Notes.
What about second question? Can anyone help?

Hi @BTTB :wave:

Indeed, there is no backward compatibility for vCenter API.
Regarding the second question, you can request here the vOneCloud appliance.