Unfortunately, there is no credible source available to prove that China is seeking approval to kill 20,000 coronavirus patients.
There is also a Singapore government agency website which reported that ABTC news cannot be trusted and cited an article published by it on 30 Jan 2020.
Moreover, China has not made any such request to the highest court to stop the further spread of coronavirus.
The COVID-19 pandemic has given rise to a lot of potentially dangerous misinformation. For reliable advice on COVID-19 including symptoms, prevention and available treatment, please refer to the World Health Organisation or your national healthcare authority.