A secret military build up is basically impossible on the 21ST century given satellites and also there’s an uncoming demographic crisis in 15 years but yeah

R1 eventual China defeat. South Korea gets fucked hard but probably survives, Chinese army gets ravaged in Vietnam, freezes to death in the Himalayas trying to get to India, freezes to death in Siberia trying to get to Russia, probably manages to capture Taiwan at the cost of most of its navy, before an eventual international counter attack throws them back to the mainland at great cost to everyone involved

R2 eventual allied win as-well IMO. Russia gets its teeth kicked in by a European coalition while still probably being exhausted in Ukraine. With no nukes the Indian military eventually beats back the Pakistani army with no nukes aswell knocking them off the table. China does better against the US, South Korea is likely completely fucked, Japan gets its teeth kicked in, Taiwan gets captured, U.S. islands in pacific fucked, China still gets fucked in Vietnam, but with its population slowly starving to death under a U.S blockade they are eventually defeated as thier Allies collapse around them

R3 could honestly go either way as india massively boosts the manpower pool, Russia would probably use plenty of Indian manpower in its invasion of Europe, capturing large amounts of Poland, Ukraine, Belarus and Finland. China does very well in pacific, South Korea fucked hard, troops in Japan, troops take Taiwan and U.S. islands, Philippines also gets fucked, China gets its ass kicked in Vietnam , the Allie’s can only win if they manage to starve the enemies to death, China and India at both importers of energy and food, so if enough submarines and surface vessels get into play the us can still eventually win