Icy Installer has been out of scene for quite long time. But its good to see it back. It is a perfect Cydia alternative for iOS 11, iOS 11.2 and iOS 11.3 and amazingly does not require jailbreak for installation of Cydia tweaks.
Apple File Conduit 2 was Cydia tweak by Saurik to access Apple iOS root file system. Unrestr1ct0r or Unrestr1ctor is a free Apple File Conduit 2 alternative that works on iOS 11, 11.1.2, 11.2 and 11.3 and does not require jailbreak. After its installation, you can proceed with iFunBox utility.
Its been quite a while since iOS 11 jailbreak was released. Though Saurik has not yet updated Cydia to support iOS 11.1.2 jailbreak, but good news is that most of the Cydia tweaks are updated by their respective developers to support iOS 11, 11.2 and iOS 11.3.