How do I Delete photos on one device only

Hi

If you are using iCloud Photo Library, then it is normal for deleting a photo on one device to also delete it from iCloud and from any other device that is using the service. This behaviour cannot be changed.

Otherwise, follow the instructions here to delete photos:

Delete photos on your iPhone, iPad, and iPod touch - Apple Support

More information:

iCloud Photo Library - Apple Support

Get help with your iCloud Photo Library - Apple Support

You can disable iCloud photo syncing (chews up a ton of memory anyway) and use something else. I personally use flickr, which has an auto upload function, so that you can delete off a device and still have the photo backed up online.

So, short answer, find a third party application that has more versatility to allow you to share/access photos between devices without the iCloud 'delete it off everything' issue.