If after hours of research you still cannot flash the device, consider:
Within GSM-Forum, navigating to the subcategory or using the search bar with the query "Coolsand cpu flash tools" reveals:
Technicians often encounter chipsets like the series (e.g., RDA8851, RDA8853). These CPUs are unique because they do not always adhere to the standard flashing protocols used by major brands like Samsung or Qualcomm. Consequently, generic tools often fail to recognize these devices, necessitating specific "Coolsand CPU flash tools."
Unlike Samsung’s Odin or Qualcomm’s QPST, Coolsand never released an official, public-facing flashing suite. Most tools were: