In this topic, I'll show you, how to get bootloader unlock code by official way.

(tested on Huawei Ascend P7).
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You will need:
Huawei Phone/Tab
Huawei ID (easy login with Facebook or create now account)
Product model, Serial number, IMEI, Product ID (I'll show you how obtain this info later)
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Gathering information about you phone/tab (PM, SN, EMEI, PID):

1) Product model
a) Take your phone/tablet
b) Go to options
c) Scroll down to section "About phone"
d) Note your Model number (first line) - HUAWEI P7-L10, etc.

2) Serial Number
a) Look on the phone box (see image below)

3) IMEI
a) Look on the phone box (see image below)

4) Product ID
a) Open your dialer
b) Call *#*#1357946#*#*
c) PID will show on your screen

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Putting info to Huawei Bootloader Unlock Site:
a) Open this page:
b) Log in to Huawei ID, if you already not
c) Set product type (phone or tab)
d) Put PM, SN, IMEI and PID to right boxes
e) Solve Captcha
f) Press Submit
g) The unlock code appears under captcha (red text, something like: Your unlocking password is：87XXXXXXXXXX5492)

And that's it, you have your bootloader unlock code!

IMAGE OF BOX (IMEI AND SN):
look this picture 

Quick update for everyone stuck in the Need phone account!

I miss placed my box and only had the phone to work with! I was trying with the serial number that I found in Settings -> About -> Status, but that is just wrong... Also registering account with my email Kept on saying just that error!

As suggested in this thread, I Logged in using Facebook and then it showed me My Serial Number and EMEI do not match;
then I went digging into service menu and found the Actual serial number.

Dial: *#*#2846579#*#*
It will present you with the service menu, then go to Option: 2. Veneer Informations > 4. Other info
You will see your Serial number AND EMEI number there...

Another question is,

what is AT LOCK and FASTBOOT LOCK ?

(found them with the Dial: *#*#2846579#*#* )

How To Unlock Bootloader On Huawei Devices

Step By Step Guide

→ First read the Pre-Requirement section carefully.

• First Open the Huawei Bootloader Unlock request page on your Computer then login to your account.(register if you don’t have an account)
• Agree to the terms and condition and click  Next button. (read carefully)
• On the next page, provide the required information about your device and hit Submit button.
• If everything is correct, you’ll get a unique 16-digit bootloader unlock password for your device.
• Now connect your Huawei device to the PC with a USB cable.(Give it required permission)
• Boot your Huawei device into bootloader mode using the following command:

adb reboot bootloaderadb 

└ If your device doesn’t boot into bootloader mode, then disable Fastboot function from your device’s Settings.

• Once your device is in bootloader mode, issue the following command to unlock bootloader:

fastboot oem unlock your-unlock-password

└ Replace the unlock Code with the Red text

• The bootloader unlocking process will start automatically.
• Once the process is finished, your device will reboot.

→ If you have any question related to this post then feel free to leave that in the comment section below.