If you return a face-down creature to its owner’s hand, the token will be a face-up colorless 2/2 creature with no name, no abilities, and no creature types. (The face-down creature card will be revealed to all players as it leaves the battlefield.)

If the copied creature had in its mana cost, X is 0.

If the copied creature is a token, the token created by Supplant Form copies the original characteristics of that token as stated by the effect that put it onto the battlefield.

If the copied creature was copying something else, the token enters the battlefield as whatever that creature was copying.

The token copies exactly what was printed on the creature and nothing else (unless that creature was copying something else or was a token; see below). It doesn’t copy whether that creature was tapped or untapped, whether it had any counters on it or Auras and/or Equipment attached to it, or any non-copy effects that changed its power, toughness, types, color, and so on.

Any enters-the-battlefield abilities of the copied creature will trigger when the token enters the battlefield. Any “As [this creature] enters the battlefield” or “[This creature] enters the battlefield with” abilities of the copied creature will also work.