I got this to work on iPhone 6 8.4 JB and my existing game was still there.
Force close the app on your phone Download the .ipa file and install using iFunBox (make sure AppSync is installed on your phone). Download the .deb file and copy onto your phone I used SSH to run the command manually since iFile isn't supported. SSH into your phone and type 'deb -i com.laxus.simcity_1.4.4-1_iphoneos-arm.deb' without quotes if for whatever reason, you want to remove the hack file, just run 'dpkg -r com.laxus.simcity' without quotes in your SSH terminal Go to your settings and find the hack and enable all features. Open Simcity Buildit. If the game is crashing, try and collect items or move the map as soon as you can.
One thing I've noticed is that this hack never gives me unlimited SimCash. Keys and Simoleons always works.
Edit2: I take it back, somehow SimCash maxed out randomly. Took several hours