What would cause an administrator to encounter a remote device backing error while running vMotion?

A cluster of vSphere 6.5 and 6.7 hosts all have identical hardware. VMs are created on the 6.7 hosts with virtual hardware version 14. During routine maintenance on the 6.7 hosts, the VMs are unable to migrate to the
6.5 hosts.
Why are the VMs unable to migrate to the 6.5 hosts?

What happens within the network when a customer uses a vSphere Distributed Switch (VDS) and vCenter is offline?

What are two features of the CPU scheduler? (Choose two.)

An administrator runs vSphere Infrastructure in the following configuration:
* Single vCenter
* Multiple data centers
* Multiple clusters under each data center, all with identical hardware The administrator wants to use host profiles to manage the hosts.
Where should the administrator attach the host profile?