To make iFile work on iOS 9.3.5, a jailbreak is mandatory. Because iOS 9.3.5 is "signed" for many legacy devices, users typically utilize tools like Phœnix to achieve the necessary root access.
If you are not jailbroken, you must use a signing tool on a computer (Windows/Mac) to install iFile. ifile ipa ios 935 work
Many users report that iFile crashes on startup or asks for a license on iOS 9.3.5. To make iFile work on iOS 9