Bad news..Xiaomi Locking Bootloader for Mi Devices:

We’ve locked bootloader for Redmi Note 3 since its launching in order to protect user data safety. As we said before, we’ll be making the same change for other Mi devices gradually. Now, the list will include Mi 4c and Mi Note Pro also.

If you’re not famaliar with the situation, please read the following explanation.

Special Note: This situation only applies to MIUI China Developer ROM for now.

Why did Mi lock the bootloader for Mi devices?
Mi is an international brand now, but it’s only in few countries currently, and is still in the stage of expanding its international market. So it’s difficult for users from countries where Mi is not officially sold to buy Mi phones. Many users have taken the risk of buying from a unofficial reseller. But they sometimes get fake Mi phones, or Mi phones with unofficial ROM loaded with bloatware. You guys must have seen some users asking in the forum whether their Mi phones are genuine, or that they have weird ROM version installed on their new phones. This is really bad for user experience, and it might even cause property loss if some malware are installed. This situation also exists in China market.

Another problem Mi users have often encounterred is that, after their Mi phones are lost or stolen, the person who got the device could easily flash a new ROM into it, and makes it almost impossible for our users to get their phones back. In the recent MIUI developer version update, we’ve add a feature that needs users to enter their Mi account info to use the phone after doing a full wipe. But if an ill-intentioned person knows how to use fastboot method to flash ROMs, this will not stop him/her from gaining control of the phone.

Based on the above two reasons, we’ve deciced to lock the bootloader. We’ve also made changes to Mi Cloud’s ‘Find Device’ function, and adjusted system update’s verifying logic.By these combined methods, user data can be better protected, and user experience can also be improved.
What will change after locking bootloader?
Locking bootloader will not affect normal OTA updates
ROOT will be disabled if user has enabled it before. Enabling ROOT will need to unlock bootloader
Recovery mode is changed. Updating via Recovery will need to use Mi PC Suite
Devices with locked bootloader can not update using Miflash. Users need to unlock bootloader if they want to flash Fastboot ROMs.
Isn’t locking bootloader against Mi’s ‘geek’ spirit?
Locking bootloader is aimed to provide better user experience, which we’ve been trying to do the whole time. In the meantime, we’ve provided a unlocking tool for senior users who know their ways around flashing and tweaking their devices.

The unlocking process is really simple. After unlocking, the device can do all the things as before we locked bootloader.

The unlocking procedure will need Internet access to get the unlocking password. Also, the Mi Account logged in on the Mi phone and the unlocking tool needs to be the same. Otherwise the unlocking request will be denied. This will ensure that ill-intentioned people will not get access to your personal data.
Final note, if you don’t know that much about Android, flashing, custom ROMs etc. It’s not recommended for you to unlock the bootloader. It might cause serious damage to your device or personal data.
Source-http://en.miui.com/forum.php?mod=viewthread&tid...