I forgot my 28-character Recovery key,how can I regain access or recover the key

A recovery key is a computer-generated, 28-digit, random character string; very few individuals on the planet could possibly “remember” it, even for a short period.

You would have had to record it on something — because you were required to re-enter it into your computer manually via the keyboard — so maybe that fact might help you remember where you saved it.

Question: Are you trying to restore access to your Apple Account; or attempting to reset a forgotten Mac password ?

Did you try to use the Account Recovery process to gain access again to your Apple Account?

How to use account recovery when you can’t reset your Apple Account password - Apple Support