Photo albums
How can I move photos to a separate album and then delete them from my “all photos” album without having them delete from my new separate album?
iPad mini, iOS 12
You can't do this.
Albums in iOS work not like albums in a traditional way, but as 'tags' if you like. You can organise photos in Albums for better experience, but cannot remove them from "All Photos". If you delete a photo from this album, it will be deleted from the device.