Is COV-19 just one thing? And will different sub-groups react differently?

Factual Questions
1

As I understand it, “serotype” just means that you get immunity from things with the “same serotype”? In which case cow-pox and small-pox were two genotypes of one serotype?

Do we know at this stage that there is only one COV-19 serotype? Do we even know if a COV-19 infection will give good immunity? And do we know that all the existing cases are from one genotype?

Also, flu and corona virus infections sometimes lead to a “cytokine storm,” a result of an extremely complex interaction between the virus and the different individual components of the immune system, both systemic and at the site of the infection. Are we at a stage where we can assign different kinds of immune response for /any/ virus, in /any/ population subgroup?

2

It started out as one thing, but by now it’s likely that mutations have occurred. Whether these are of sufficient magnitude to call them “different things” is going to be difficult to assess for a new virus like this one. Some viruses tend to mutate more easily than others, and I have no idea where this particular virus ranks on how stable it is.

3

I have not analysed them myself but hundreds of the latest nucleotide and protein sequences are openly available; it takes only a moment to draw a phylogenetic tree and to examine the differences in detail. E.g., if you know what you are doing you can run BLAST on it.