Corporeal Projection

The term "defending player" in the myriad rules (or any other ability of an attacking creature) refers to the player the creature with myriad was attacking at the time it became an attacking creature this combat, the controller of the planeswalker the creature was attacking at the time it became an attacking creature this combat, or the protector of the battle this creature was attacking at the time it became an attacking creature this combat.

Effects that cause you to pay more or less for a spell will cause you to pay that much more or less while casting it for its overload cost, too.

Any enters-the-battlefield abilities of the copied creature will trigger when the token enters the battlefield. Any "as [this permanent] enters the battlefield" or "[this permanent] enters the battlefield with" abilities of the copied creature will also work.