I believe "921 Rocket" is a Western designation and not used by China. The official name is currently CZ-5DY, with Xin Yidai Zairen Huojian (New Generation Crewed Rocket) used in the past.
A model of China's next generation of manned launch vehicle, the Long March-10, displayed in Beijing.
🔥 CASC conducted a hot fire test of YF-100K kerolox engine on July 22, to power the moon landing mission rocket Long March 10 (c) CCTV