Can't turn on iPhone, no backup and updating isn't successful. Is there anyway to retrieve the data?
Disk Drill or iFunbox may be able to help. It is evident that you are able to access the iPhone for a restore, so Disk Drill is likely the best choice. 

Disk drill will create the best backup that it can with the files left unencrypted, and iFunbox will only be able to access whatever the phone can.

Best of Luck!