My huawei S7-721u is bricked. It is stocked at boot. I have tried to flash different update.app rom but unsuccesfull because it can't be turned into recovery mode. But I think and pray for it that it can be flashed through Sp flash tool. Since I have been searching for it I did found an Sp flash tool rom for my device to flash with it.
I read something about working with update.app to a flashable rom with SP Flash tool here: (http://forum.xda-developers.com/showpost.php?p=54603809
) but when I followed all the instructions, I still got stocked at step n. 12 since the -preparefile.exe is missing in the folder.