Everybody knows the real number of cases is greater than the confirmed number of cases, everywhere, regardless of what country is reporting the numbers.
Nobody knows. Anybody that cites numbers is pulling them from a very biased sample. With the exception of a few countries, most of the testing is done on a very self-selected set of people. Those with symptoms who were ill enough to get tested and willing deal with a with a 14 day quarantine if they turned up positive.
Even counties with good, pervasive testing can’t test for how many people already had it and are carrying antibodies.
We are flying very blind here. Treat all numbers with a huge grain of salt.
No it's about knowing how diseases spread. This is not a new disease. the mortality rates come from the ratio of known deaths to known infections. Obviously not all cases are known especially in the USA where we don't even have enough tests to test people coming in with severe symptoms.