I think what is key is that they figured out how to make a virus from a “vaccine”. So yes, backwards.
I would definitely speculate that they had the “vaccine”, first. It’s why we have only the one. They got an RNA sequence generating the spike they wanted. In the lab, they have solved mRNA generation and delivery. They use it to show that the sequence they have can induce the spike they want in living cells.
They then get colonies of animals, like bats, breeding a naturally occurring coronavirus. They give the mRNA to the sick bats. Some cells in some of the animals are going to try to combine the two sequences. Some will succeed, producing really sick bats. You find the virus you think you want and breed it in colonies, too. You can do gain of function, at this point, looking for really, really sick bats.
Eventually, you have a nice, matched set. Your super virus and it’s “vaccine”.
Downsides:
The mRNA delivery isn’t really made for “vaccinating”. It can work in a lab but has bad delivery side effects on living beings.
Your “vaccine” has a limited interval of use. The virus is going to mutate in the wild and your forced “blending” of genetic material is probably its least stable. The same goes for any “gain of function” you tried to breed into it.
I’m off to buy more tinfoil.
I’m off to buy more tinfoil
You are not even close to being wrong.