As Apple's servers release a new update, automatically the oldest version of iOS at the time no longer available. With the launch last Monday of iOS 14.5.1, Apple stopped signing iOS 14.4.2, a version that launched at the end of March.
This movement occurs one week after the release of iOS 14.5, a version that has introduced support for AirTags, the possibility of unlocking the iPhone with the Apple Watch when wearing a mask, as well as the long-awaited tracking lock function that has been talked about so much on Facebook.
Once Apple stops signing an older version of iOS, no longer possible to download, install and verify the installation through Apple's servers, the only solution being to install the latest version available at that time or the immediately previous one (if it is still available).
In this way, if today you have to restore your device, the only solution is to install iOS 14.5 or iOS 14.5.1. Apple always allows a reasonable time before removing previous versions of iOS to verify that there is no compatibility problem.
When everything is verified to be working as planned, Apple removes the old versions from its servers to protect customers from vulnerabilities that have been patched in the most modern versions of the operating system.
Currently, Apple is working on iOS 14.6, a version that currently is in the second beta for both developers As for users of Apple's public beta program, an update that is not expected to bring big changes, since it will probably be the last update that iOS 14 receives before the launch of iOS 15, a version that we will begin to know at WWDC 2021 that it is celebrated at the beginning of June.