Software update required to connect iMac to iPhone

This is a followup to the "missing" photos from the "Recents" folder after syncing an IOS device with an older iMac.

Since another user on my iMac has an iPad Pro running IOS 15.4 I decided to sync his photo library with the iPad as another test. Before syncing, I opened the Messages app on his iPad and while writing a message I brought up the "Photo" link within Messages to attach a photo, his entire Photos library was available. After syncing, and choosing "include photos from the past year" the snyced photos were no longer available from within the Messages app. The "past year photos" DID appear in the Photos app "Library".

In addition, when connecting the iPad to the iMac, the same "software update required" box appears, and again the software update downloads, then attempts to install and then gives the "install failed" notice. Because exactly the same thing occurs with two different IOS devices when syncing, this is clearly a change made by Apple regarding the software needed to sync the older OS iMac limited (by Apple) to Big Sur with devices running IOS 15.4 and newer, that results in an odd displacement of the "Recents" photo albums that are linked to the Messages and Mail apps. Hopefully this can be resolved by future attention to the software changes.

I have reviewed all the steps in the "if you see an error..." link. My Mac has the latest version of Big Sur (newer Mac OS's are not supported) and the iPhone has iOS 15.4. I did plug the phone directly into the iMac, and restarted both. I do not use any third party security software. I still get the same "Installation failed" box after the "download" and "install" windows appear with their slider lines. No error code exists on the "failed" message box (see above). I have looked at the "allowed" incoming connections on the firewall settings and all Apple related items are allowed. In Finder, the "Restore iPhone..." button brings up the "an update is needed...." window, and since the update fails, there appears to be no way to get beyond this loop. I can sync the iPhone and change the Photos loaded on it successfully, but the "Recents" folder will not load anything that is on the iMac.

Thanks for the tip. I did create a test user account and when connecting the iPhone the same "download message" appeared. The download works fine and the install box comes up but then I get the "Install failed".

I also tried installing from my iMac's Admin account. Same result.

What I am trying to solve is:

I periodically copy all the photos taken by my iPhone into my Photos app library on the iMac, and when I do that I select the option to erase those photos from my iPhone. Then I sync my iPhone and iMac using "Finder" with the the Sync process set to include the last years' worth of photos in my Photos app library to the iPhone. This process seems to work as it always has, but when in Mail or in Messages on the iPhone and I want to attach a picture to the email or message, the selection for Photos will only show those photos taken on the phone since the last sync. The "Recents" folder under Photos will not include the photos synced with the iMac. The Photos app on the iPhone will show all the synced images when "Library" is selected but the "Recents" album will only contain those photos taken since the last sync. Only the Photos "Recents" folder appears to be accessible from Mail or Messages. My work around is to open Photos on the iPhone, then select the image I want and copy it, then go back to Mail or Messages and paste the photo. Not a real solution. I was hoping that restoring the iPhone OS might solve this problem, but I cannot get past this "Installation failed" issue to do that.

I did check on my iMac that in Photos the "Recents" folder does contain all my photos, ordered by the most recent photos first. However when syncing, that folder does not appear to transfer to the iPhone. If I specifically check that folder in the syncing process, then my entire Photos library is transferred to the iPhone, which is also not a workable solution.

I am not a user of iCloud for anything and am not inclined to have yet another database to keep track of.

Any thoughts on this issue would be appreciated.