[Xiaomi Redmi Note 3 Guides, News, & Discussion] Rishab kaushik:
This post is refined version of my Miui forum's post.

Decryption error, unknown baseband, Wifi issues, IMEI NULL after downgrading, custom rom installation or any other messing up?

Then you're at the right place .

NOTE: This guide is only for Snapdragon version. Bootloader unlocked not necessary.

The first thing to address is Decryption error, This is due to Miui default encryption. To recover from this error you have to goto TWRP( You should know bcz Decryption error occurs after installing custom rom and custom rom needs TWRP ) and format data in wipe options.

Now here comes the part to recover imei, efs and baseband

Things you will need

1. Miui 8 marshmallow fastboot romhttp://bigota.d.miui.com/V8.2.3.0.MHOMIDL/kenzo_global_images_V8.2.3.0.MHOMIDL_20170425.0000.00_6.0_global_d25b57383a.tgz

2.MiFlash tool Latesthttp://en.miui.com/thread-345974-1-1.html | Please disable driver signature before installing to install drivers successfully.

4.IMEI repair and EFS recovery tool + adb (attached below)

5.EDL zip (Put rn3 in fastboot and run reboot file from this zip after extraction)( Attached)

6.ZCX TWRP https://www.androidfilehost.com/?fid=24727332921017084

7. Bootloader unlock zip(extract it)https://xdaforums.com/attachment.php?attachmentid=4057737

Unlocking bootloader(Skip if already unlocked)

1. Put rn3 in fastboot then edl.

2. Open miflash tool and browse to the bootloader unlock zip( Select the folder extracted)

3. Now click refresh and flash( If any "non-hlos" error occurs put non-hlos file from "stock fastboot ROM images folder" to unlock zip's images folder.)

Unlock done.

We're now going to flash stock ROM and restore modem and efs files.

1.Extract the fastboot rom (2 times,firstly the tar file and then the file that is in the extracted folder). It is must to extract the rom in root of C drive so that the path of the extracted files do not contain any spaces.

2.Open Miflash tool

3.Put RN3 in fastboot mode

4.Open efs+adb+IMEI folder.

Press shift inside the folder and click open command

window here (adb terminal)

Type

fastboot erase modemst1
fastboot erase modemst2
fastboot erase fsg
fastboot flash modemst1 modemst1
fastboot flash modemst2 modemst2
fastboot flash fsg fsg

5.Now browse ROM folder (Present in the location where you have extracted the rom ) from Mi flash tool.

If drivers properly installed Mi flash will recognise the device.

6. Click refresh and then Flash.

Wait for 10-15 mins, miflash will show success. Reboot the device by holding power button.

7. Check device's Imei, baseband and networks.

8. If IMEI is still null follow the guide hereafter else use your device as earlier and rate this post.

IMEI RECOVERY

1.Boot into fastboot

2.Flash ZCX TWRP (Extract the zip and run the batch file named "╡τ─╘PC╢╦╦ó╚δrecovery" or something)

3. If phone doesn't automatically boot to twrp press vol up+power button.

4. If language is chineese, change it to english( a Google search will definitely help you)

5. Now in TWRP goto advance->supersu->install->Reboot.

6.

5.Connect your RN3 to pc and turn on usb debugging, open the adb terminal(use the efs folder)

6.Type the following and accept the permission on the device.

adb shell
su
setprop sys.usb.config diag,adb

7. Now the device is in diagnostic mode and made sure it is listed in the device manager as Qualcomm HS-USB Android DIAG 901D, If not update the driver by manually browsing to the ports category of the installed drivers.( Sometimes phone doesn't goto diag mode in miui, the workaround is to install a custom ROM and root it and run the above commands.)

8.Open efs+adb+IMEI folder and run WriteDualIMEI(W+G_eMMC) ..

9.Type Both the IMEI from the box or invoice and click Write

10.It will show Pass .

11.You have successfully flashed the IMEI

12.Reboot and check IMEI(*#06#).

If there are still issues with networks but Imei is ok you need to flash qcn file.

FLASHING QCN FILE

1. Download this QCN ZIP and extract.

2. Download Qualcomm qpst tools.

3. Follow this guide from further steps.

https://www.google.co.in/amp/s/xdaforums.com/redmi-note-3/how-to/guide-qpst-tool-backup-imei-nvram-t3455297/amp/

I'm giving credits to all those people whose work I've consolidated for my post and sincerely thankful for the work done by them. Here are some of them

IMEI+EFS-------http://xdaforums.com/member.php?u=7469310

DualIMEI WRITER-----Archelot http://en.miui.com/space-uid-1597338059.html

ZCX TWRP-----http://www.miui.com/thread-4395191-1-1.html