How do you do a hard reset for Mac with no password?
How do you do a hard reset for Mac with no password?
How do you do a hard reset for Mac with no password?
Regarding the lost password, please see: If you forgot your Mac login password - Apple Support
As to the "hows" of resetting the Mac, please see the "Related Article" linked above your post.
Also, please take a look at: What to do before you sell, give away, or trade in your Mac - Apple Support
How do you do a hard reset for Mac with no password?