The latest iTunes beta no longer allows iPhone and iPad users to reinstall the older iOS version, which is what we generally call “downgrade”, but don’t be nervous, this is caused by bugs. Apple’s policy of downgrading the iOS system has not changed.
Downgrading to the previous iOS version requires installing an IPSW file on your mobile device. These files are from Apple and are only available in newer iOS versions. For example, you can currently downgrade from iOS 12.1.3 to 12.1.2 or 12.1.1, but you can’t downgrade to an earlier version.
iTunes software is required to install IPSW on iPhone or iPad, but the latest iTunes 126.96.36.199 beta bug caused users to be unable to complete this operation, so those who want to downgrade iOS should avoid installing this beta version.