(Posting this in the forum for the current iOS, because it doesn't apply to any specific older iOS version.)
If you have an old iOS device that cannot upgrade to the latest iOS and you try to download an app from the App Store that's no longer compatible with your iOS version, the App Store sometimes offers you to download the last compatible version of the app.
After I discovered Overcast on my iPhone 11, e.g., I could also download it for my old iPhone 5 that's stuck on iOS 10 even though the latest version of Overcast requires iOS 12.
Obviously, this doesn't always work—sometimes the app is too new and there has never been an earlier version that's compatible with your old iOS, and sometimes the developer blocks the download of old versions, because they have known security vulnerabilities or because they would no longer work anyway (due to server changes), even if you still had them installed.
What I could not find out is whether there's a way to check if earlier versions are still available, if you don't have an old device to try it out. Case in point: I have been offered an old iPad Air with iOS 12 and would like to know if the apps I need would work on that device. Some of them require iOS 13 (at least their latest versions). However, I don't currently have an iOS 12 device. Can I somehow find out if earlier versions compatible with iOS 12 are still available?
If you have an old iOS device that cannot upgrade to the latest iOS and you try to download an app from the App Store that's no longer compatible with your iOS version, the App Store sometimes offers you to download the last compatible version of the app.
After I discovered Overcast on my iPhone 11, e.g., I could also download it for my old iPhone 5 that's stuck on iOS 10 even though the latest version of Overcast requires iOS 12.
Obviously, this doesn't always work—sometimes the app is too new and there has never been an earlier version that's compatible with your old iOS, and sometimes the developer blocks the download of old versions, because they have known security vulnerabilities or because they would no longer work anyway (due to server changes), even if you still had them installed.
What I could not find out is whether there's a way to check if earlier versions are still available, if you don't have an old device to try it out. Case in point: I have been offered an old iPad Air with iOS 12 and would like to know if the apps I need would work on that device. Some of them require iOS 13 (at least their latest versions). However, I don't currently have an iOS 12 device. Can I somehow find out if earlier versions compatible with iOS 12 are still available?