I'm from Uzbekistan; is it okay to go to China via South Korea? I don't have a visa for South Korea but I have a China visa and I have prepared a China health code in my country.
While visa may not be required for short-time international airside transit, current Chinese regulations require a health code from the original departure country as well as the last transit point before the flight to China. Incheon does not have international airside testing facilities that would satisfy the current requirements of the Chinese Embassy in (Rep. of) Korea, which require two tests, at least 24 hours apart from each other, within 48 and 24 hours before scheduled departure. You must enter Korea and stay for at least 2 days before the transit to China can be authorized by the Chinese embassy. A Korean visa is then required.
The Chinese government has issued new directives in the entry requirements so the Embassy may adapt the requirements soon. However, it is always your responsibility to determine the rules that are effective at the time of your travel.