Are any of the bellow chemical changes reversible? If yes, then how?

Question

Mixture of Lear Nitrate and Potassium Iodide
Mixture of Copper Sulphate Solution and Iron
Mixture of Copper Sulphate Solution and Sodium Carbonate
Mixture of Dilute Hydrochloric Acid and Magnesium
Mixture of Dilute Hydrochloric Acid and Calcium Carbonate
Mixture of Dilute Hydrogen Peroxide and Maganese Dioxide

Answer 1

What do you not know that keeps you from answering this question?

Answer 2

I know that all of this are chemical changes and mostly all chemical changes are non reversible. However, there are some that are reversible. I'm just not sure if any of this ones are reversible or no.