Check the Information Topic.

This is a double battle with no time limit. There are no banned moves, and the arena is the Tiny Tourney Indoor Arena; a medium sized, dome-like arena in a canary yellow colour. As a result, weather-based attacks will not work.

Coin flip tells me Dark Dragonite selects first; Crystal Tears will attack first. Any queries on which Pokemon you feel can be eligible, just PM me; but if you want to be safe, stick with first-stage and non-evolvers.