Please learn the difference between "common cold coronaviruses" and specific viruses with specific characteristics.
There are 4 specific viruses known as HCoVNL63, HCoV229E, HCoVOC43, and HCoVHKU1, which are commonly referred as "common cold" coronaviruses. So it looks like that you don't know what you are talking about here.
We know a shitton about it. For example we know the current dominant strain is already a genetic mutation from the previous one that hit Wuhan, and that re-infection of the original strain as well as this first mutation is not possible. We also know there are several other genetic mutations which have amounted to nothing due to not being easily transmittable or aggressive.
LOL... Is this the Dunning–Kruger effect?
First of all, there are many mutations of SARS-CoV-2, which are wildly spread. Most naturally occurring mutations have no functional consequence for the virus, i.e. they do not affect virulence, pathogenicity, or immunogenicity. Therefore, they are considered different lineages of the same virus. The D614G mutation in the spike protein is the only known mutation so far that potentially affects virulence of SARS-CoV-2, and therefore, we speak about two different strains of SARS-CoV-2 while many different lineages exist.
Second, as demonstrated in the aforementioned studies, reinfection with the same strain is possible. In fact, it was something that was suspected in a few cases before, but it was never conclusively demonstrated, because without complete genome sequencing, it is impossible to exclude a possibility of resurgence of the initial infection that was not fully cleared. Unfortunately, many popular publications confuse words "lineage" and "strain", so they reported it as "re-infection with a different strain of the virus" while it was just a different lineage.