DC Challenge was an experimental limited series published from 1985 to 1986. Each chapter was written by a different author (and drawn by a different artist), and would end in a cliffhanger which the next creative team would have to resolve.
DC Challenge was intended to be "continuity free" and does not fit into the canon of Earth-One, the mainstream DC universe of the time. However, for simplicities sake, we have indexed it as if it happened on Earth-One, instead of creating a new universe for the story. Similarly, when the story crosses into Earth-Two, Earth-S, etc. in later chapters, it's not the canon versions of those realities either