To revert now impossible.
Apple no longer signs iOS 11.4. The operating system cannot be installed on a compatible iPhone and iPad. Usually the company ceases to distribute the previous version after about two or three weeks after the release of the updates. It happened this time — iOS 11.4.1 was released on 9 July.
Owners of iOS devices running 11.4 can no longer revert to this firmware version if you encounter problems or in case of a failed upgrade attempt. In recovery mode now also installs iOS 11.4.1, so be careful.
Stop supporting older versions of iOS — one of the tools in the Cupertino use to motivate users to install the updates. Updates contain current patches and security features. In iOS 11.4.1, for example, there is a USB mode to Restricted Mode to protect against password guessing.
On the other hand, the latest version of the firmware does not yet support jailbreak. If you plan to hack your iPhone or iPad, it is better to refrain from upgrades and use the iOS 11.4. Now Electra jailbreak only works with iOS 11.2–11.3.1, but in the future the developers can add support and penultimate version of the operating system.