It's a tricky and challenging question, but Jack is Garland in Stranger of Paradise: Final Fantasy Origin. Therefore, Jack is also Chaos, but at the same time, he isn't. The Jack Garland we see in Stranger of Paradise is the original Jack, meaning that this was pre-Chaos Jack Garland. Eventually, upon uncovering his identity and his past, his lust for vengeance drove him to absorb the Soul of Chaos. An entity pulled Jack Garland back in time, precisely 2000 years before he entirely takes on the persona of Chaos. To put it shortly, the Stranger of Paradise: Final Fantasy Origin happens before Jack Garland could establish a time loop, as seen in Final Fantasy 1. We can assume that this is a prequel to the first game.