Help! I accidentally turned on icloud for Photos on my phone, and it says it will delete all my photos if I turn it off

Thanks Muguy! My concern is the notice I got when turning on Album sharing, seemed to imply it turns on iCloud Photos sync at same time, and will delete everything when I turn it off.

I actually figured it out, with confirmation from Apple Support...

Turning on Album sharing only turns on album sharing, and will delete shared albums FROM THE PHONE when I turn shared albums off. If I understand correctly, it does not delete them from the icloud library, unless DELETED ON THE PHONE (or another device synced to the same library) prior to turning off syncing shared albums.

The notice I received when turning on album sharing gave me the impression that library syncing had been turned on, and stated all photos would be deleted from iCloud when syncing was turned off. It seems this is not the case... (I wish such notices were clearer... a user was frustrated to no end when being asked for confirmation of some action with a password, not knowing that it was the device password, not the apple ID password he was using to no avail, which sent him down the wrong rabbit hole thinking he needed to reset the apple ID password when it did not work etc etc... avoidable with clearer messaging...but I digress, and will let apple feedback know... similarly notices relating to icloud libraries could be more erudite)

Something that did happen when I turned on album sharing is that older shared albums, re-appeared on my phone from the master library in icloud.

But my iPhone 12 Pro Photos Library remains independent of Photos in iCloud. Phew. Nice to be able to share albums, from a library which is not synced in its entirety to iCloud.

However, I do have the iPhone Photos entirely backed up, and this is sweet too. Under iCloud device backup, the iPhone 12 Pro Photos library is included in device backup data.

(iPhone Settings > Apple ID > iCloud > iCloud Backup > Backup this iPhone turned on > All device Backups - iPhone > Backup details - Photo Library is turned ON.)

Next I am going to see if a shared album I create on the iPhone, if I can share it with myself, so that the album appears on iCloud Photos, and Macbook Pro Photos... with all the tags, favouring, etc... something I lamented did not get carried over when I imported photos from iphone to macbook Pro.

Anyways, I have a solution and understanding that I did not have before, and hope sharing here can help someone else faced with similar constraints and confusion.