I have tried and failed to upgrade from Android 4.2 to 4.4 on my Lenovo B6000-HV. At first using OTA method; Error in the middle of process and I have to flash with stock ROM to make it working again. Then I tried to put the files on micro SDcard; The error was
failed to update.
Go to Recovery and Clear cache and Dalvik.
Reboot and Check for OTA.
Backup all data to any external storage (Apps and data).
Factory Reset device.
Check for OTA.
Install Custom Recovery and Custom Kitkat ROM from XDA.