Rolling back system or App updates is not an option. The only available versions of Apps are those that can be installed from the Apple App Store; as Developers update their Apps, prior versions are replaced with the current release.
As for backups, while App data will be included within the backup, the App itself if not included; Apps are simply re-installed from the App Store where the App remains (a) compatible and (b) available for the target device. Finally, an iTunes or iCloud backup can only be restored in its entirely; selective restore is not an option.
The tags appended to your iPad suggest that you have an iPad Air with iOS12 installed. The first generation iPad Air, iPad mini2 and mini3 can only be updated to iOS 12.5.7.
Apple ended major update support for these models of iPad in September 2019 - although they have continued to receive occasional “point” security updates, the most recent being released January 2023. These devices cannot be updated to iPadOS 13 (or any later major versions of iPadOS) as the internal hardware does not meet the minimum technical requirements (CPU capabilities and available RAM) for newer versions of iOS/iPadOS.
The majority of App developers have dropped support for iOS versions preceding iOS 13.x for technical reasons (often because APIs or software libraries upon which they rely have been updated in the new version of iPadOS, making their App incompatible with earlier versions).
Whilst many App titles remain compatible with your iPad, if you want or need to access to Apps requiring more recent versions of iOS, you’ll need to consider replacement of your iPad with a newer or current model that supports iPadOS16/17.
For information, here is a list of the highest version of iOS supported by the older models of iPad (for simplicity - “generations” are shortened to a number) that are restricted in their ability to be updated:
32-bit devices (obsolete)
iPad1 - iOS 5.1.1
iPad2, iPad3 and iPad mini1 - iOS 9.3.5 (WiFi Only models), iOS 9.3.6 (WiFi & Cellular)
iPad4 - iOS 10.3.3 (WiFi Only), iOS 10.3.4 (WiFi & Cellular)
64-bit devices
iPad Air1, iPad mini2 and iPad mini3 - iOS 12.5.7
iPad Air2, iPad mini4 - iPadOS 15.8
iPad5, iPad Pro (9.7"/12.9" first generation) - iPadOS 16.7.2
Newer models are all able to be updated to the current version - iPadOS 17.1.1
- iPad Pro 12.9" (2nd generation and later)
- iPad Pro 11" (1st generation and later)
- iPad Pro 10.5"
- iPad Air (3rd generation and later)
- iPad (6th generation and later)
- iPad mini (5th generation and later)
