These are the instructions to root Micromax Ninja A91 smartphone (running on android 4.0) using the KingRoot App.
Requirements: Your Android Device should have at least 20 percent of device battery and internet access to begin the root process.
Congratulations! Your device is now Rooted. You can verify the root status using any Root Checker app from the Play Store.
[*] No data loss process: Your Android Phone Data like contacts, pictures, videos, music, etc. will not be affected by the above method.
[*] Warranty Void: Your Android Device Warranty may be Void after following the above method.
[*] How to unroot? If you want to unroot the Android Device, then head over to How to remove Kinguser App page.
[*] Replace KingUser: After Rooting the device using the Kingroot, you will get a Chinese SuperSU app called KingUser. If you are not comfortable with the Chinese KingUser App and want to replace it with the official SuperSU App, then head over to How to replace KingUser App with the SuperSU page.
[*] Micromax Stock Firmware: If you are looking for the original Stock Firmware, then head over to the Micromax Stock Firmware page.
[*] Micromax USB Driver: If you are looking for the original usb driver then head over to the Download Micromax USB Driver page.
[*] Credits: KingRoot Application is created and distributed by Kingroot Studio. So Full Credits goes to them for the Application.