@MoinakBhattacharya-9823 Apologies for the delay in response.
Yes, Internet access is enabled by default in VMs inside a VNet so you can connect to Azure Services from pool of Virtual Desktop.
Coming to your second query the Spring Update already uses ARM. In Fall the feature is not available but it doesn’t matter since you only need Internet connection to access the resources.
Moreover the current version of Windows Virtual Desktop is integrated with Azure AD for getting the access to the resources and AD or AADDS for entering the VMs so you don't need to worry on that part.
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