Yes you can do all of that, but it’s saved as a separate asset that is not related in any way to the original. That’s the issue. Also, it would be nice to be able to do these things in the web app as well.

As for syncing, if all your phones are logged into Immich as the same user, you wouldn’t have any issues syncing photos. I don’t thing Immich currently allows sharing assets between users. That can be troublesome for family albums.