Gain of Function research is very much real and not a secret. People can, and do, debate the ethics of it, but that debate doesn't change the fact that it's been going on for a while and continues today. I'm pretty sure influenza viruses are a pretty common one they do this with, but if the place in Wuhan that specializes in studying coronaviruses was found to be doing GOF research on coronaviruses, that wouldn't exactly be surprising.
One of the major issues people on the "GOF is bad" side of the debate raise is that by intentionally making viruses more dangerous, we are increasing the risk of accidentally starting a deadly pandemic and killing millions of people, despite the original intention which would have been to study how to protect ourselves against such a virus.
So for me, if I'm looking at your list Crouton, bullet points 1 and 4 are both on near equal footing in terms of plausibility in my own mind. 2 and 3 I have to agree are pretty hard to believe though.