Re: Can used Win 7 ESU license from CSP Program on previously Win 7 Pro from COEM ?
Yes, for the ESU license it does not matter in which channel the Windows 7 license was obtained in.
The details are in the Product Terms, this is where the terms for CSP licenses are also been published.
Only the "Windows 7 ESU for M365" has prerequisites, but this is not available in CSP anyway.
Page 44 of January terms:
2.12 Windows 7 ESU (Extended Security Updates)
Customer may acquire Windows 7 ESU licenses on a per device basis. Devices running a local OSE covered by ESU or accessing virtual OSEs covered by ESU must be licensed with Windows 7 ESU for the respective year of coverage. Devices do not need an ESU license to access Windows 7 OSEs covered by ESU running on Windows Virtual Desktop on Azure. Windows 7 ESU 2020/2021/2022 for M365 licenses may only be assigned to devices with active Software Assurance or used exclusively by users with Windows Enterprise, VDA, or M365 SLs. Windows 7 ESU 2020/2021/2022 licenses may be assigned to any device. Windows 7 ESU 2021 & 2022 and Windows 7 ESU 2021 & 2022 for M365 licenses may only be assigned to devices also licensed with ESU(s) for the prior year(s).