Apple No Longer Signing iOS 14.4.2 and iPadOS 14.4.2, Stops Downgrades from 14.5 and 14.5.1
You can no longer downgrade to iOS 14.4.2 or iPadOS 14.4.2 as Apple is no longer signing the said firmware. Here is what you can do.
You Can No Longer Downgrade to iOS 14.4.2 or iPadOS 14.4.2 as Apple has Stopped Signing the Firmware
Apple has stopped signing the iOS 14.4.2 and iPadOS 14.4.2 firmware for both iPhone and iPad. What this means is, you can no longer downgrade to said firmware anymore if you have updated to the new iOS 14.5 / iPadOS 14.5 or iOS 14.5.1 / iPadOS 14.5.1. The interesting thing here is that you can jump between 14.5 and 14.5.1 as both are being signed by Apple currently.
At this point, sticking around with an older version of Apple's firmware is not a good idea either. Apple patched a crucial WebKit flaw that could have been actively exploited. Apart from that there are tons of performance related improvements in the new updates as well. If you still decide to stick with it, then it is entirely your call. But keep in mind that you cannot install iOS 14.4.2 or iPadOS 14.4.2 if you have already update to either 14.5 or 14.5.1 updates.
I will go as far as saying that actively making sure that your device on the latest firmware is the right thing to do at this point. You can check if there are available updates by going to Settings > General > Software Update on both your iPhone and iPad.
While you are here, check out the following: