Redmi Note 3 Marshmallow Update MIUI 18.104.22.168
If you are unable to update your Redmi Note 3 to Marshmallow version then you can download official update from here. The update file is available in both Recovery and Fastboot version.
Recovery Update:- Download Recovery update zip file and open updater then click on 3 dots then you see Choose Update package. Then browse for the file and phone will reboot into recovery.
Fastboot Update:- Download Fastboot update file and extract it. Then flash it with MI Flash Tool.