I am not saying China purposely spreading the virus they just didn't try too hard to stop it from spreading to the world either, why do you think in the beginning China ban all travel domestically but not for Chinese leaving the country, trump himself said it also
Banning travel at that point is pointless anyways. There are cases in Europe and the US since November last year. There are articles on that in the covid thread
No country had ever managed to stop the spread of new diseases in history. Did the US stopped the swine flu? You are asking for way too much.