It’s not a complete version and yes there are several bugs as well. Also Mi 2/ 2s are 2 years old now, which makes them a rare phenomenon outside China. Mi 2 was introduced in 2012 and features 4.3 Inch HD display, 1.5 GHz Quad-core CPU, 2 GB of RAM and Adreno 320 GPU.
The new ROM has English language support also but we are not sure if this will be compatible with international variant of Mi 2 or 2S. As for official availability, Xiaomi has confirmed Android 5.0 Lollipop update for only Mi3 and Mi4 as of now.
Other phones to get Android 5.0 update include Nexus devices, Android 5.0 Lollipop is confirmed to arrive on HTC One M8, Sony Xperia Z series, LG G3, LG G2, Samsung Galaxy S5, OnePlus One, All Motorola Phones, GPe Devices and Android One phones. Source