So Meliodas used his OG Magic in Danafor, Against Zeldris’s girl and Galan.
And he was probably about to use it against Dolor and Gloxina.
I don't think he used it in Danafor, nor against Gelda or Galan. The only occasion when Meliodas might have used a glimpse of his OG Magic, is when he injured Ban. This page obviously indicates that, and debunks the claim that the flames of Purgatory are the cause of Ban' scars.
I think Ban's first two panels are clearly implying that.
1- "
Having come to Purgatory, it's clearer now than ever". By this, he meant that before coming to Purgatory, he was actually suspicious of the "real" thing that caused those scars on his "immortal" body. We can say that he wasn't satisfied with the claim that the Flames of Purgatory are the thing which caused the scars.
While after coming to Purgatory, he became certain that it wasn't the Flames, nor the ice of Purgatory; as they fail to leave even a small scratch on his body. He concludes then:
2- "
You've got some crazy strength". I think it is definitely a foreshadow of Meliodas' OG Magic from Nakaba.