iOS 9.3.5 is the last version of iOS 9 available to some devices such as the iPad 2, the iPhone 4 etc and was originally released to close a very big venerability which meant devices could be hacked remotely. For some time it seemed as though this iOS version would be left unjailbroken however today using an Exploit by Siguza, realkjcmember and tihmstar 9.3.5 can be jailbroken and supports all 32 bit devices.
This is a big deal for users of devices such as the iPhone 4 because even if you mess up your jailbreak on this final version you know you can simply restore and re-jailbreak, the jailbreak itself is semi-untethered meaning you will have to re-jailbreak once the certificate expires.
To Jailbreak simply go to https://phoenixpwn.com and Download the IPA.
Download Cydia Impactor from here.
Connect your device to your computer. (Always make a backup)
Start Cydia Impactor and drag the IPA onto the top field.
Enter your Apple ID credentials.
On your device, go to “Settings > General > Device Management” and trust the certificate.
Run the app and tap on “Prepare For Jailbreak”.
Wait for it to respring, then launch Cydia from the Home Screen.
Whenever you reboot, open the app again and tap on “Kickstart Jailbreak”.
Whenever the app expires, install it again with Cydia Impactor.
Exploit might fail a few times, if it does just try again.
I’m sure we will see paid signing services host this iPA soon meaning the certificate will last longer, in the meantime you can access a mirror copy here if the above site becomes too busy.