Thanks for the information, I regret that I left some details out since I wish for it to be as simple and easy to reply to as possible.
I have fixed the discrepancies between devices syncing to iCloud.
I have no vpn, or corporate profiles, my network settings have been rest in the past 24hrs, alongside the devices software settings reset you suggested.
The memory of all devices are sufficient too.
The issue resides in these areas IOS, device rerouted code due to lacking AI feature of flagship models 15 Pro+, or index issues.
devices were left on permanent screen time for 8hrs with the photos app connected and syncs confirmed.
I have logged out and on of iCloud on all devices.
Yet the current iPhone 15 IOS18.5 model I use index search in the photos app and this does not return a result or more than 1 image however it has before June 25 and this was a correct returned result.
If I use the index search in the photos app on my iPhone X IOS 16.7.1.1 this however does return a correct result to searches. (They are both in a communication range of IOS, but the X cannot update further without hindering further performance issues from software).
anyone have any ideas please do let me know, I don’t have access to an MCR, Laptop or developers kit atm so don’t necessarily wish to remove my Apple ID to test if it could fix via this route.