I was looking for an answer from a trusted source. These are the known facts: 1. According to the Haynes Guide: The CBR250R was designed by Honda engineers in India in 2010. It was first producing and launching in the Thai market in 2011 (in the guide, page 0*7, in the first column on the left, down below). 2. The Honda vehicle book does not mention two various models of engines. 3. My motorcycle license (the model marketed for the European market) lists an MC41E engine, and it is written that the entire motorcycle (not just the engine) is manufactured in Thailand.
According to unofficial sources, MC42 is manufactured in India? And maybe MC42 refers to the first series made in Thailand at 2011? It's really not clear.