[Issue] HTC Desire 816 Unlocking bootloader

[AC Question]

Hi All,

I am trying to unlock bootloader in htc desire 816, as i read from blogs i got a Unlock_code.bin file from HTC then i tried "fastboot flash unlocktoken Unlock_code.bin" after this it's gives a pop up in my htc phone with YES and ON option i select YES then phone goes to recovery mode and i received the following error :-

E: missing bitmap oem_unlock_bg (Code-1)
E: missing bitmap oem_unlock_bg_yes (Code-1)
E: missing bitmap oem_unlock_bg_no (Code-1)
Write host_mode success
handle_cota_install: Can't mount /sdcard, 1 times
handle_cota_install: Can't mount /sdcard, 2 times
handle_cota_install: Can't mount /sdcard, 3 times
handle_cota_install: Can't mount /sdcard, 4 times
handle_cota_install: Can't mount /sdcard, 5 times

and i can see as "LOCKED" in the bootloader.
The issue is my HTC 816 keeping on rebooting automatically every 30 seconds( Don't know why) so trying to put custom ROM so that may be this issue can be resolved.

I have tried factory reset But nothing is working, neither factory reset nor any other option from recovery.
i don't get any error while doing wipe data/factory reset at last it says data wipe complete but when i reboot my phone everything is same. all my setting and apps are still installed.
According to me, the issue is "Whatsapp" app(may be some issue) because of this app my phone keeping restarting. I tried uninstalling in the 30 second window but when i uninstall it shows as uninstalled but as soon as my phone reboot and i check again whatsapp is there.
So no data is been deleted/uninstall.

Please do HELP!

Thanks in advance.