May I have a basic difference between UEM and Dynamic Environment Manager if any?
Are you meaning the change from UEM to DEM , in 9.9 the name changed.
VMware Dynamic Environment Manager Release Notes 9.9.0
or do you mean
Unified Endpoint Management (UEM) | Workspace ONE | VMware
if you mean the latter think of DEM like a user management tool and UEM as a computer management tool.