Downgrading or Upgrading to Apple’s iOS 11.2.5 is not possible. Just a few days after the release of iOS 11.2.6 in a bid to fix the Telegu character text bomb bug, Apple stops Signing iOS 11.2.5.
Yes, you get it right, as the stoppage of signing iOS 11.2.5 will cause the users be unable to downgrade or upgrade to iOS 11.2.5, and the users will get Error 3194, “This device is not eligible for the requested build” if the users try to install iOS 11.1.2 using iTunes.
Downgrading of the iOS software update can be useful where the previous iOS software update can be jailbroken. In case of facing problems after upgrading to the latest iOS software update, some users prefer downgrading back to the older version.
Apple’s stoppage of signing iOS 11.2.5 firmware file does not come as a surprise, as over the previous few years, the giant has used this strategy to let the jailbreakers stay at bay.
Apple does not only release new software updates to fixes the vulnerabilities used by the jailbreaks, but also it stops signing the older iOS firmware file to prevent its users from downgrading back to the older iOS version that is able to be jailbroken.
Jailbreakers are recommended to stay on iOS 11.2 – iOS 11.2.2, by coolstar. They are also recommended to avoid upgrading to iOS 11.2.5, as the giant Apple seems to have made numerous changes on the security side in iOS 11.2.5.
Also, it is not possible to jailbreak iOS 11.2.5, so it’s not such a big deal that Apple has stopped to sign iOS 11.2.5.
In case you have saved the SHSH2 blobs using future restore, you are lucky enough to be able to always downgrade to an unsigned iOS firmware like iOS 11.1.2.
At the moment, it is not impossible to jailbreak iOS 11.1.2 or lower using Electra Jailbreak or LiberiOS jailbreak.
iPhone X got successfully jailbroken on iOS 11.2.1 by the security researchers, but they have also said that they do not plan to release any jailbreak. So it still remains to be seen if any one in the jailbreak community is able to discover the exploits & he does release the much-awaited iOS 11 jailbreak.
In case you are on iOS 11.1.2 or lower then it, you are always advised not to update to the latest iOS version, because it increases your chances of a jailbreak.