there is no such thing as a "Curse Plate."
bug attacks
Underground!
Arceus (With Dragon plate)
Yes, in the old chateau, but it is called the "insect plate".
a fist plate
you can get iron plate by using explorer kit
purple
Bug Bite, which is a bug type move, and pluck
you have to dig it up when you are underground
if a Pokemon holds a plate (arceus) and a Pokemon uses flail the shards restore the plate because flail breaks the plate.
no there is no such thing as the polychromatic plate