Renminbi is simply the name of China's official currency, meaning people's currency, issued and managed by the People's Bank of China, with the Yuan serving as its base unit and Kuai as the everyday informal term for it. The term stayed in the news through 2010 mainly because of the ongoing trade tension between China and countries like the United States, which pushed for the Renminbi's exchange rate to be allowed to rise, arguing that China was holding it artificially low to keep its exports cheap and competitive. This exchange rate dispute was a recurring economic story of that year.
The other three descriptions are invented and do not match reality. No such Volkswagen car project priced under the Tata Nano existed under the name Renminbi. Brazil's real aerospace success story is Embraer, not a company called Renminbi built to rival Boeing and Airbus. And while regional economic cooperation is discussed within ASEAN, there has been no single ASEAN currency proposed under this name similar to the Euro. The currency explanation in option 1 is the correct one.