To unlock and root Redmi Note 3, you'll need to install Developer ROM, which will wipe all data and files on your phone. Therefore, it is suggested to back up your phone data via built-in backup function as well as other backup methods for Android phone.
Part 1. Back Up Before Root Redmi Note 3
Step 1. On your phone, go to Settings> Additional settings(in SYSTEM & DEVICE)> Backup & reset> Local backups.
Step 2. Choose Back up, and then choose the data you want to back up.
Step 3. Tap Back up to start.
Step 4. Once the backup completes, connect your phone to a Windows PC.
Step 5. Open your phone memory via Windows Explorer.
Step 6. Find the MIUI folder> backup> AllBackup. All your local backups should be here with the name of date.
Step 7. Copy the backups you need, and then paste to PC.
Note: Your photos and videos may not be included in the backup. You can move them to your PC manually or upload them to Mi Cloud.
Part 2. Install Developer ROMStep 1. Visit to http://en.miui.com/download-301.html. On Developer ROM section, click Download Full ROM.
Step 2. Move the downloaded zip file from computer to your Note 3 root directory.
Step 3. On your phone, find and open Updater. It is in Tool folder on the Home screen by default.
Step 4. Tap the menu icon on the top-right corner and choose "Choose update package".
Step 5. Find and select the zip file, and then tap OK.
Step 6. Wait the update to complete.
Part 3. Unlock BootloaderStep 1. Visit http://www.miui.com/unlock/index_en.html, and log in with your Mi account.
Step 2. Unlock Now button to apply for unlocking permission.
Step 3. Fill in the information in order to pass the application. It may take 1-3 days for Xiaomi to give you the permission, so you can apply before installing Developer ROM in order to save time.
Step 4. Download and install the Mi unlocking tool on your PC.
Step 5. Connect your phone to PC and unlock bootloader with the Mi unlocking tool.
Part 4. Open Root Permission on Redmi Note 3Step 1. On your Redmi Note 3, open Security app.
Step 2. Tap Permissions> Root access.
Step 3. The system will warn you the risk of rooting your phone. If you have made your mind, choose Yes from the start to the end.
Note: Even after you root your Note 3, apps that require root access may won't be able to get root permission. You need to go to Security app> Permissions> Root access, and then you should find the apps that recently requested for root access. There are switches beside them. Tap to give or disable root permissions for apps. You'll be alerted for 5 times whenever you want to give root permission to an app.
Part 5. Restore Backup to Redmi Note 3Step 1. On your phone, go to Settings> Additional settings> Backup & reset> Local backups.
Step 2. Choose to back up some of the apps. In this way, the system will create the folder for backups, which is the only way for the phone to recognize the backups that we moved to PC in Part 1.
Step 3. Move your backups from PC to your phone under MIUI folder> backup> AllBackup.
Step 4. Back to Settings> Additional settings> Backup & reset> Local backups. Now the system should detect the backups we made in Part 1.
Step 5. Choose the backup you need, and then tap Restore.
After rooting Redmi Note 3, you can enjoy it freely. Most importantly, you'll be able to recover data from your phone after accidental deletion.