See inline
In Room OS - Is it necessary to have an CVI license to attend/host MS Teams Meetings?
>> Yes if you are using Cisco as the CVI provider you need a license for Cisco CVI.
In MTR mode - Do we need the device licence to attend /host Webex Meetings?
>> The webex meeting since you are a guest and as you are invited to a meeting then you don't need a license to attend - because you are a guest in that webex meeting. The host inviting you needs a webex license.
In MTR mode - Do we need device licenses to manage the device in the control hub?
>>> Yes you need a device license for control hub registration, analytics, troubleshooting, templates, software upgrades etc.
Thanks
ashish