How to roll back the firmware Xiaomi Mi 9T: expert guide

Owners of Xiaomi Mi 9T (also known as Redmi K20) often face a situation where after the next update the system starts to work unstable, the battery runs out faster, there are sudden reboots, and the interface slows down where everything used to fly. The only right solution in this case is to return to an earlier, stable version of the software, which is technically called a downgrade.

The firmware rollback process is a complex operation that requires strict sequence and risk understanding. Unlike a regular update that a user can run in one click, returning to the old version is often blocked by the manufacturer for data security reasons. You will not only need to download the correct file, but also possibly unlock the bootloader if you plan to switch between the global and Chinese versions.

In this guide, we will take a look at all the available methods for returning software on your device, and we will discuss preparation, tool selection, and a step-by-step algorithm that will help you resuscitate your gadget without going to the service center.

Risk assessment and device preparation

Before you start any manipulation of the system partition, you need to realize that downgrade is not a regular procedure. Android security system often prevents you from installing an older version on top of the new one to prevent vulnerabilities. If you try to install the old firmware on top of the new one without first cleaning, the phone can go into an endless cycle of reboots, known as bootloop.

The most critical aspect is data loss. The rollback process almost always involves a complete reset of the device to factory settings. All your photos, contacts, instant messengers and installed applications will be permanently deleted. So creating a full backup on an external medium or in the cloud is a must-do step, ignoring which can lead to the loss of important information.

⚠️ Warning: Before starting the procedure, make sure that the battery charge is at least 60%. Interrupting the flashing process due to battery discharge can lead to irreversible damage to the software part of the device.

You will also need quality. USB-The cable, preferably original, that came bundled with the device. Cheap charging cables often don't provide stable data transfer, which can cause an error in the file writing process. The computer you're going to use must have up-to-date drivers. ADB Fastboot and be connected directly to the motherboard, not through USB-hub.

Selection of the rollback method and search for firmware

There are two main ways to roll back the software version on the Xiaomi Mi 9T: through the built-in update menu (Recovery) and through the bootloader mode (Fastboot). The first method is simpler and does not require an unlocked bootloader, but it only works if you roll back to a version that is newer or equal to the one that is now, or if you move between regions of the same branch. The second method is more powerful, it allows you to completely re-mark the memory partitions, but requires an unlocked Bootloader.

Firmware files are divided into two types: Recovery and Fastboot. Recovery files have a.zip extension and weigh about 2-3 GB. They are designed to be installed through the update menu. Fastboot firmware has a.tgz extension, weighs more and contain full images of all partitions of the system. Fastboot method will also require a special utility Mi Flash Tool.

It is important to correctly identify the region of your current firmware. The global version is marked with the letters MI in the code version, the European version is EU, the Russian version is RU, and the Chinese version is CN. Attempting to install Chinese firmware on a global device without an unlocked bootloader will lead to a verification error.

Recovery Menu (No PC)

This is a good way to go from global firmware to Russian or vice versa, or to roll back one version if the system allows it. It doesn't require a computer, but requires a firmware file in.zip format at the root of the phone's internal memory.

First, download the desired firmware archive and rename it to update.zip to make it easier to search, although this is not always necessary. Place the file in the root directory of internal memory without putting it in folders. Then go to the phone settings, select About phone and click on the version of MIUI. In the window that opens, click on the three dots in the upper right corner and select Select firmware file.

Once the file is selected, the system will check its integrity, and if it's checked, the phone will suggest that you restart and start installing, at which point the screen will go out and the update process will start, and don't touch the device until the process is complete and the desktop appears.

However, if you try to roll back to a much older version, the system will give you a message "Can't verify update" or "Current version is newer." In this case, this method will not work, and you will have to use a more radical approach through the computer.

Full Downgrade via Fastboot and Mi Flash

If the standard method is blocked, the only way out is to use Fastboot mode.This method requires an unlocked bootloader. If your bootloader is locked, you will have to wait 168 hours (7 days) after submitting an application in the Mi Unlock app before you can unlock it.

To start, download the Fastboot firmware (.tgz archive) and unpack it to the root of the C disk so that the path to the folder is short, for example, C:\mi9t_global. Long paths with Cyrillic characters often cause errors in the work of the firmware utility. Next, download and install the Mi Flash Tool program on your computer.

Turn off the phone completely. Then press down and power at the same time. Hold them until you see a picture of a hare repairing an android on the screen, or a Fastboot. Connect the phone to your computer with a cable. The Windows Device Manager should have an Android Bootloader Interface.

fastboot devices

This command in the command line will help check if your computer sees your device. If the serial number is displayed, the connection is established. Launch the Mi Flash Tool, press the Refresh button, and your phone should be determined in the list. At the bottom of the window, select the firmware mode. For a full rollback, the best option is to choose Clean all, which guarantees the deletion of all data and the installation of a clean system.

Press Flash and wait until it's done. It can take 5 to 15 minutes. It automatically reboots at the end. It can take longer than usual to boot up the first time after flashing, which is normal, and it's optimized.

⚠️ Warning: Never select the "Clean all and lock" option if you are flashing a phone with a changed region (e.g., a Chinese person on the globe) that will result in a hard brick device that can only be restored through a paid account of an authorized service center.

Solving typical firmware errors

In the downgrade process, users often encounter error codes, one of the most common is Miss matching image and device, which means you're trying to flash a firmware designed for a different model. Make sure that the firmware is for Davinci (codenamed Mi 9T) and not for Mi 9T Pro (codenamed Raphael).

Another common problem is the Anti-rollback check failed error, which is rollback protection for the bootloader version. If the phone has a Level 4 anti-rollback (ARB) version and you're trying to put firmware on Level 3, the process will be locked at the hardware level, in which case you can only roll back to a version with the same or higher ARB level, or use special engineering methods that are dangerous.

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If the Mi Flash Tool gives you a Not enough space error, try renaming the firmware folder in a short name with no spaces, such as "rom", and placing it directly at the root of the C:\rom disk.

You also see the phone going into EDL mode (black screen, charging lights or nothing on) and it's an emergency boot mode, you can get out of it by holding the power button and increasing the volume for 15-20 seconds at the same time, and if that doesn't work, you'll need a deep-roof cable or a specialist.

Initial data setup and recovery

After a successful firmware rollback, you'll see a welcome screen, like when you first turn on a new phone, and it'll suggest you select a language, connect to Wi-Fi, and log into your Google and Mi Account. Don't rush to restore all your data from your backup right away.

First, let the system update its Google Play services completely. Go to your settings and check for system updates again. Sometimes after a rollback, small security patches may come that fix the bugs of a particular version. Make sure all the basic features work correctly: calls, mobile Internet, sound.

Only after checking the stability of the work can you start installing applications, it is recommended not to restore the applications in a package, but to install them again from the store, this will help to avoid cache transfer or conflicting settings that could cause unstable operation before rollback, Contacts and photos can be downloaded from the cloud.

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Clean installation of applications after a firmware rollback significantly reduces the likelihood of re-occurring software errors and system conflicts.

FAQ: Frequently Asked Questions