Sara doesn't have full functionality like siri. @Devil'sAdvocate Go to settings>generals>siri and enable it.
1)First it will not work ( It will work if you are really lucky ), go to cydia and install iFile, its free from bigboss, so you don't have to add a server.
2)Then go in the iFile to var/mobile/library/preferences, and delete com.apple.assistant.plist. NOT com.apple.assistant.support.plist, don't delete this, delete com.apple.assistant.plist.
3)Then delete the certificate and install this
certificate. Then reboot (If you check iFile again you will see that com.apple.assistant.plist has been recreated, leave it, it should be recreated)
4)Hold the home button, siri will open but not work, spam it (Keep pressing it simultaneously without speaking anything for about 5 min, then click on siri but don't speak, just leave it opened until it says "I can't seem to catch that", then you will get siri fully working!
This worked for me, but I don't know if it works for everybody.