How to install Android Marshmallow OTA update on Android One|Download Link

Android Marshmallow is an incremental upgrade and focuses largely on bug fixes. Google has introduced six new features with Android M: App Permissions, Web Experience, App Links, Mobile Payments, Fingerprint Support and Power & Charging.
Android One 1st Gen device, codename Sprout ( Micromax) : Download Link Spice : Download Link
Warning : “Installing an official update update doesn’t voids your device’s warranty, but it remains an unofficial procedure after all. You only are responsible for your device and we won’t be liable if any damage occurs to your device and/or its components.”

Installation Guide- 

1. Download the File from the link given above and transfer it to phone’s storage.
2. Now Press Power + Volume up button for booting into Bootloader Mode.
3. Now Select Recovery mode by pressing Volume Up button and scrolling.
4. Select The “Recovery” option and enter using Volume Down button.
5. Now press Again Power + Volume up button and get the Recovery menu .
6. In stock recovery, choose ‘install update from sdcard’ and now navigate to the Place where you kept the file.
7. And then select the file with power button.
8. Then Install it.When done, you will be back to main screen of recovery.
9. Select ‘reboot system now’ to restart your device.

That’s it.