Basically, the life cycle of smartphones is about two years. After that, the manufacturers stop updating the software on the devices. But, this does not apply to Xiaomi smartphones. The company tries to support outdated models, and recently updated devices even in 2014 - Redmi Note and Redmi 1S to MIUI 9.
Both devices were introduced about 4 years ago, but they were still updated to the latest version of the Xiaomi interface - 184.108.40.206. The firmware is based on Android 4.4 KitKat and has a security patch for October 2016. But, nevertheless, the new version of the shell works without problems even on such old smartphones. Both devices support all the features of MIUI 9.
Characteristics of smartphones
Recall that Xiaomi Redmi 1S originally worked for MIUI 5. The smartphone installed Qualcomm Snapdragon 400 and it has 1 GB of operating and 8 GB of internal memory. Redmi Note worked on the processor MediaTek MT6592 with a maximum frequency of 1.7 GHz and was sold in two versions: 1 GB and 2 GB RAM.