1. Only EMUs and new electric and diesel locomotives are called Harmony. This is just Chinese. In fact, the English name of Harmony EMU is CRH, China-Railway-High-Speed ??(China-Railway-High-Speed). As for old-fashioned locomotives, there are Shaoshan electric locomotives and imported models, such as 6K, 8K, 8G, etc., and internal combustion models include Dongfeng, Dongfanghong, industrial and mining, and imported models, such as 6Y, etc.
2. Shaoshan, Dongfeng, Dongfanghong, industrial and mining, etc. . 3. (Same as above)
4. The Chinese name is Harmony, but the model is different. Such as CRH1, CRH2, CRH3, CRH5, etc., which are further divided into CRH1E, CRH2C, etc. In fact, many of China's EMUs are imitations of foreign locomotives. Like China, their trains are called ICE-1, ICE2, ICE3 (example). They also have a general name, but the models are different. Japanese Shinkansen, German ICE, French TGV, Eurostar, Swedish X2000, etc.
Harmony is just a general term, just like the Volkswagen of cars. And various models, such as Lavida and POLO.
As for the name, the meaning is Harmony Railway.