This works like a charm, as you indicated! ➕
[NOTE: As a safety measure, I used iExplorer (Macroplant) first to a copy various information (contacts, messages, photos, and so forth) from the iPhone, which it does outside of iTunes, since iExplorer is a Mac app. Once that was done, I disconnected the iPhone from the MacBook. At this point, there was no Eject button in iTunes, since iTunes had not yet officially recognized the iPhone . . . ]
When you first connect the iPhone to the MacBook, there is a message asking if you want to trust the iPhone or MacBook, or whatever--and you want to trust it, which is important . . .
Once I did the iExplorer safety stuff, I used the procedure you described to get an iPhone 5s recognized, backed-up, and synced to a MacBook after the MacBook was upgraded to Yosemite. The iPhone is running iOS 7.1 and iTunes is 12.0.1.26 . . .
Deleting all the existing backups in iTunes Preferences for "Devices" was the first step and a key part of the strategy, but I also checked (a.k.a., set) the option to "Prevent iPods, iPhones, and iPads from syncing automatically" . . .
The next step was to turn-off the iPhone and restart it; which I also did for the MacBook . . .
Then, I connected the iPhone to the MacBook and clicked on "Continue" to get to the next step . . .
[NOTE: Clicking "Continue" is somewhat disturbing, since until you have done it at least once, you have no idea what is going to happen, but in this instance being bold works nicely, since there is the option to stop without doing anything, but if you stop immediately after clicking on "Continue", then you need to disconnect the iPhone; power-down the iPhone; shutdown the MacBook; restart the iPhone; restart the MacBook; and then connect the iPhone to the MacBook. It's odd, but I think it refreshes everything and clears buffers and other stuff. And since at this point there is no Eject button for the iPhone in iTunes, I just unplugged the iPhone, which worked nicely . . . ]
When you get this far, iTunes thinks it is a new iPhone and wants to do a full-backup first, which is what you want. It does not wipe the iPhone--it just does a full-backup and syncs the basic stuff . . .
Since there is no existing backup of any iPhone--because all the existing backups were deleted--iTunes does a full backup. There is the opportunity to set an option, and I selected to manage music and movies manually . . .
Once you give it the go ahead, it starts the backup and then does they sync. All the other stuff (calendar, contacts, and so forth) was set not to sync automatically, which is what you want at this stage . . .
Basically, (a) you want iTunes to recognize the iPhone as a new device and (b) you want iTunes to do a full-backup of the iPhone . . .
iTunes did the full-backup and synced the basic stuff but no music and movies, since I had not done anything to manage music and movies so far (see above and the option to manage this part manually rather than automatically) . . .
Once that stuff finished, iTunes successfully recognized the iPhone as one of its devices, and then the iPhone can be ejected, or you can set the various detailed options for syncing and so forth; apply the new settings; and do a new sync . . .
This was an iPhone that had never been connected to a Mac other than what happens at the Apple Store or whatever when you purchase an iPhone . . .
Everything was there after doing this, and the iPhone was not zapped or whatever . . .
Thanks for the excellent advice! 🙂
P. S. As another earlier part of the strategy, I cloned the MacBook primary drive to a LaCie d2 Quadra external drive using SuperDuper! (Shirt Pocket) and then verified that it was a bootable clone by booting from the LaCie drive and then ejecting the Mackintosh HD primary MacBook internal drive, which worked nicely . . .
The upgrade to Yosemite was done on the MacBook primary internal drive (Macintosh HD), but if it was necessary to rollback the clock, I could boot from the LaCie external drive, which is important, because the LaCie external drive has the older version of iTunes and all the existing backups at that time . . .
It nearly always is good to be able to rollback the clock when doing upgrades and all that stuff, and the combination of SuperDuper! and a second hard drive (which for a Mac Pro can be an internal drive) makes this possible . . .
