@microsoftintuneautopilotnoob, Thanks for posting in Q&A.
For Autopilot devices, to reset it, we will do Autopilot Reset. Here is a link with more details:
https://learn.microsoft.com/en-us/mem/autopilot/windows-autopilot-reset
For your second question, it seems the error is with device limit. Please check on both Intune and Azure AD device limit restrictions to see if we have set the limit as 5 there. Here is a link we can refer to check the restrictions for your reference:
https://learn.microsoft.com/en-us/mem/intune/enrollment/device-limit-intune-azure
Hope the above information can help.
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