Where Some Ideas Are Stranger Than Others...
So, You'd Like to Reinstall An Old iOS App (2018-01-06)
Okay, fair enough, if you don't, in which case, feel free to skip this thoughtpiece completely. For the rest of you out there, I thought it was only decent and fair to write up how I managed to do this, because the application that went awry for me is one that I like very much, but it has become wildly buggy on the latest version of iOS on my incredibly old but still chugging second generation iPad. Originally I was completely stymied as to how to sort out the issue, especially when a full restart, reinstall, and a couple of gesture tricks that sometimes shake things loose all failed. (The newer iOS versions can trigger odd gesture problems in older applications – or the older applications can trigger odd gesture problems in the newer iOS.) Then my luck finally ran out in the grim world of iTunes, and my library became so utterly corrupted I had to trash the lot and reimport all my music and apps. This rendered my music library into a complete shitshow that still hasn't finished stinking (no, I'm not bitter), but did lead to a surprisingly useful thing.
I found myself with a handful of older and newer versions of my purchased iOS apps. Unfortunately this did not include preservation of my very few in-app purchases. Word to the wise folks, if you have an in-app purchase, the developer screws off somewhere, and you have to reinstall the app, your in-app purchases are gone and irretrievable, so far as I can determine. This may not be a real risk for most, but, for what it's worth, there is my warning. I'm actually less irritated about the loss of a small in-app purchase as compared to the mess my music library is in.
Anyway, as igeeksblog.com noted, on older devices, you can sign in to the iOS app store and reload older versions that can still run on an older version of iOS. This worked great when I needed to restore my even older iPod with the few apps I still use on it, and kudos to apple for making the process transparent and easy. The big problems came down for the iPad, because it can officially run the latest version of the application in question, so the app store will not offer any older version, even as a "Well, we don't agree with you at all, and it's on your own head if it all crashes. Don't call apple support, they will laugh at you. You suck. Fine. Here it is." sort of option. That would be a very rude option, but still, as a last resort, bearable. The folks like me whose cell phone service provider's system sign off sounds utterly disgusted with you for ever checking your voicemail will recognize the style.
(For those wondering why I don't just submit a bug report, the difficulty is that the software company has retired all development and support for this version of the app, and based on other tests I have worked through, the bug is on their end not iOS's and I don't need the mass of features in the latest version of the app which I would have to purchase at full price.)
The folks at igeeksblog.com suggest digging around in your iTunes backups, or asking a friend if they have a copy of the app. Except, logically I don't think you could use your friend's copy, because it will be watermarked for your friend's iTunes account, not yours. So, best to stick to a copy from your own backups. Then you just have to drop it into your app library in iTunes, click "ok" when it complains you're replacing a newer version, then drag and drop it onto the icon for the iDevice you are working with. However, it turned out in my case that the oldest version of the app I could pry out of my iTunes backups had the same problem as the most current version. I was close to giving up. But then I found myself wondering about my Time Machine backups. By some wild chance, could there be an earlier copy of the app wedged in there somewhere?
The answer is yes, but the key is to dig around starting from the top level of your home folder. If you start from the Mobile Apps folder in your iTunes folder itself, Time Machine will insist you have no backups whatsoever beyond the current year. This is a strange and unnecessary behaviour, and may be a bug. After all, if you purchased the app there really should be no issue, and I have happily used this app for years. In any case, after a couple of reinstalls of successively older versions of the app, I finally have a working version again. All you have to do on locating an older version in Time Machine is restore the older version, then follow the same directions as the igeeksblog.com article linked to above provides.
Hopefully the likelihood of anyone else seriously having to do this is very small. However, iTunes is such an alarming and lumbering behemoth you really can't count on that forever. The best thing to do is to back up all of your music, apps and so forth on a separate drive as well as taking advantage of Time Machine. I back up my music independently of Time Machine, but had not done the same with my apps since this particular combination of issues had never occurred to me as a possibility. Alas, it is always the most creatively weird things you never thought of that cause the most headaches.