There are not tests which can differentiate one coronavirus from another
Of course there are. We have completely mapped the RNA of covid-19. Are you referring to field tests of infected people? You should be more clear, or you're right, others won't be able to follow.
But even if that is what you meant, you're still wrong. Yes, the tests identify covid-19, not just an infection of a virus from the Corona family.
There are no tests to differentiate an acute infection from a previous exposure
No idea what this nonsense means or how it is relevant. I doubt you do, either.
If you are immunocompromised or malnourished take whatever precautions your health care provider ordered but don't demand that the nation be brought to standstill.
Actually, they do. Scientists recommend precisely this, to slow the exponential growth of the number of cases, so that our hospitals are not overwhelmed. But you're about to post your crack research that shows otherwise, right?