I want to keep all original photos and videos on iMac, not icloud without disabling icloud
[Re-Titled by Moderator]
Provided you do not optimize storage your originals remain on your Mac, yes.
By default, that is what happens when you sync any file unless you turn on optimize photos or optimize files in photos settings and your Mac iCloud settings respectively
I have a function (optimize storage etc) on iMac selected to store originals in it - is it right?
How to store original photos and videos on iMac while using iCloud
