1) Only 8th generation Intel processors are supported at this time.
Windows 11 supported Intel processors
2) It comes down to security (TPM 2.0) as a primary driving factor. A lot of older chipsets can run TPM 2 (virtually) but it really isn't TPM 2.0 hardware.
Windows 11 requirements
https://learn.microsoft.com/en-us/windows/whats-new/windows-11-requirements
About TPM 2.0
A good article on why Microsoft is not supporting older than 8th gen processors (some of it is speculation so be aware of this)
https://www.howtogeek.com/739029/why-doesnt-windows-11-support-my-cpu/
If this helps please mark as correct answer.