Troubling problem with iTunes backups of iPhone

I had a problem restoring an iTunes backup over the last few days. Ultimately, I was successful, but I am troubled. I want to describe what happened so (1) other people might benefit from what I tried, and (2) someone can tell me exactly what happened, since I'm still not sure.

Short story: I keep backups of my iPhone and iPad both on my Mac (enrypted, roughly weekly) and in iCloud (approximately nightly automatically). I went to restore my iPhone from my Mac, and found the password didn't work. I was able to get the iPhone restored from iCloud, but (due to another problem I'll describe) I couldn't restore all the apps the way they were. Plus, I couldn't rely on the Mac backups and I couldn't even remove and change the password for FUTURE backups unless I wiped the phone clean.

I learned a lot.

I have an iPhone 6 Plus, and I wanted to pay off my AT&T Next installment plan so I could unlock the phone. AT&T gave the OK, but after I dug a little deeper, I found you need to back up and restore the iPhone in order to have the SIM unlock "take." Pain in the neck, but relatively straightforward, I thought. I had an iCloud backup from 2 in the morning, and proceeded to make a fresh Mac backup. I always leave encryption set so the iPhone restores passwords, health data, and other items. So far, so good. Then I wiped the phone, and went to restore. iTunes told me I had the wrong password. Of course, I tried it 5 times, rebooted everything, tried again, and panicked. I did some research, discovering that people in my situation are generally told they must have changed the password at some point and forgot it. [I use a different password for each on-line services, but I use the same password for my Mac, my iPhone, and my iPad, and I use that same password to lock the backups. Always have. The Mac's keychain showed that the backup password was what I thought it was.]

So, I went back to a Carbon Copy Cloner backup of my system from a few days before all of this, running that as the boot drive, and lo and behold, that also said the password (to a slightly older backup) was wrong too.

Panic continues.

Note that the iPad password was fine -- no problems there in any event.

I purchased Elcomsoft's password cracker. Ran it on my Mac under Parallels, since only the Windows version can crack passwords. Ran the small brute force, nothing. Then I decided to create a cracker file with hundreds of passwords I've used over the past several years in case one of those was the password. Ran it -- guess what -- the password was exactly what I thought it was. *NO* extra spaces or symbols or mix-ups -- it's EXACTLY what I thought it was.

The only thing I can think of is that the Elcomsoft software did something that eliminated some corruption in the backup file -- some corruption that had been there from before and carried forward in subsequent backups.

Word to the wise -- as always -- don't trust your backups. Verify them regularly to make sure they work as you expect. Apple doesn't make this easy, since you basically have to wipe your phone to be able to see if the backup works.

A side note: One of the problems with my iCloud backup is that I changed my iTunes store e-mail address a while ago. Some software was purchased under the old address and some under the new address. I thought the address would change everywhere, but it turns out that when I restore the iPhone, I need to enter the password for both accounts. Great -- but the account with the old e-mail address doesn't exist. So, after going all over the web, I found a workaround. One must start the iCloud backup, and enter the password for the current iCloud account, then, only when prompted for the password for the old account (which is the same password), one must log in at applied.apple.com, CHANGE the e-mail address on the account and save, and then, once that validates, restore the e-mail address to the one you wanted. If you don't still have control over both e-mail addresses, I don't know what you do, because you are asked to verify both e-mail addresses (old and new).

Phew.