Let's start off with a pretty easy round, shall we?
We have been in the midst of a heat wave here, so all I can think of right now is how hot I have been and ways to cool off.
R1. A hot dragon: Bingo! - Ember
R2. A cold dragon: Bingo! - Frostbite
R3. A dragon that breathes fire: Bingo! - Hellfire
R4. A dragon found only in the Volcano biome: Bingo! - Royal Crimson
R5. A dragon found only in the Alpine biome: Bingo! - Ridgewing
Co-op1. Use your dragons to spell the word “heat” – play