@Kent CHEN Thanks for posting in our Q&A.
For Q1: Before you do this action, it is suggested to check if there are duplicate devices under Devices > All devices in intune portal. If yes, please check if duplicate devices' "Managed by" both shows "intune".
For Q2: It depends on if they are actually checking in. If the device isn’t actively being used, the selective wipe may not occur until the next time the app opens.
For Q3: It is not supported to rename BYOD devices in intune.
https://learn.microsoft.com/en-us/mem/intune/remote-actions/device-rename
Generally, it is suggested to name your BYOD devices before enrolling to intune.
Hope it will help.
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