Who’s in control?!

I’m confused. In S4 we learn that Henry finds the Mind Flayer sentience and forms it himself to be under his control, helping him achieve his hive mind influence. But in The First Shadow play we see that young Henry encounters the Mind Flayer in dimension X and gains his powers from it. So what came first? What is the actual timeline here? I’m seeing a lot of theories saying Vecna is trying to break free from the Mind Flayer now but isn’t he controlling it? Hasn’t that always been the plot? Maybe I’m remembering things wrong but is anyone else confused too?!