Xiaomi Redmi 1S has a 4.7″ 720p IPS LCD display, Snapdragon 400 chipset with quad-core 1.6GHz processor, 1GB of RAM and 8GB internal storage. It has an 8MP shooter with 1080 video capture capability, and is powered by a 2000mAh battery. As with all Xiaomi Android smartphone devices, the Xiaomi Redmi 1S runs Xiaomi’s own user interface, MIUI, on top of Android 4.3 Jelly Bean.
Xiaomi Redmi 1S is unlike to get official Marshmallow support as it falls in the low-end category. However there are many teams who work on making custom ROMs for this phone. An unofficial version of CM 13 is available for this phone which will update it to Android 6.0. A detailed guide to install this ROM is given below.