What is RCEP and why did India deny to join the trade deal?

India had opted out of RCEP and the main reason was China. But what did the country do? Here is a detailed report on same.
Union Home Minister Amit Shah on Monday said India’s decision to not join China-backed mega Regional Comprehensive Economic Partnership (RCEP) deal is a result of "PM Narendra Modi's strong leadership & unflinching resolve" to ensure national interest in all circumstances, adding: “it shall ensure support to our farmers, MSMEs, dairy & manufacturing sector, pharmaceutical, steel & chemical industries”.