Important:
Backup all your data.
Paste "SuperSU-v2.78-201609011115.zip" to external storage of phone.
1.Install both the drivers(windows 7)(It should be successfully installed all drivers,If already installed then leave this step)
Steps for driver installation in windows 8,8.1 and 10 users:
Click the Start Start menu and select Settings.
Click Update and Security.
Click on Recovery.
Click Restart now under Advanced Startup.
Click Troubleshoot.
Click Advanced options.
Click Startup Settings.
Click on Restart.
On the Startup Settings screen press 7 or F7 to disable driver signature enforcement.
Your computer will restart and you will be able to install non-digitally signed drivers. If you restart your computer again the driver signature enforcement will be re-enabled.so don't restart again before successful installation of both drivers
2.Download sp flashtool and Marshmallow Stock ROM(Link for CPN3) and extract them using 7zip
3.Open SP flashtool
4.Click Scatter Loading then select scatter file from extracted stock ROM folder.
5.Click on download -> switch off your phone and connect to PC
6.Wait till below green popup appears
7.Now disconnect your phone
How to root:
8.Download the below scatter and TWRP recovery files:
MT6753_Android_scatter.txt
Recovery
9. Open spflashtool folder and paste "recovery.img" and "MT6753_Android_scatter.txt" files into spflashtool folder.
10. Now right click on "flash_tool.exe" and run as administrater,after flashtool start,click on "scatter loading" and select "MT6753_Android_scatter.txt" .
11. Click on "download"(on left top side with green colour icon in spflash tool).
12. Now switch off phone and connect to Pc via USB cable.Press twice the volume up button. A slider will run on bottom of spflashtool. If everything fine then you will see a pop up with green tick.
13. Disconnect phone from PC. Press Volume up and Power button till recovery comes on the screen(This is important step,don't boot into normal mode,after flashing recovery you have to direclty go to recovery mode by pressing Volume up + Power button similtaneously).
If you get Unmodified System Partition warning then swipe right to allow modifications.
14. Select "Install"
15. Select SuperSU-v2.78-201609011115.zip file
16. Swipe right to confirm flash
17. Reboot the device.
18.If you found no superSU app on reboot,then reboot to recovery and flash superSU again.
19. check root status with any root checker app.
10. Now right click on "flash_tool.exe" and run as administrater,after flashtool start,click on "scatter loading" and select "MT6753_Android_scatter.txt" .
11. Click on "download"(on left top side with green colour icon in spflash tool).
12. Now switch off phone and connect to Pc via USB cable.Press twice the volume up button. A slider will run on bottom of spflashtool. If everything fine then you will see a pop up with green tick.
13. Disconnect phone from PC. Press Volume up and Power button till recovery comes on the screen(This is important step,don't boot into normal mode,after flashing recovery you have to direclty go to recovery mode by pressing Volume up + Power button similtaneously).
If you get Unmodified System Partition warning then swipe right to allow modifications.
14. Select "Install"
15. Select SuperSU-v2.78-201609011115.zip file
16. Swipe right to confirm flash
17. Reboot the device.
18.If you found no superSU app on reboot,then reboot to recovery and flash superSU again.
19. check root status with any root checker app.
Now voila!Phone is rooted.Cheers.
