Answer:
1: A salt plus hydrogen gas
2: Yes, the metals which react with cold water are; sodium, calcium and potassium. Magnesium does not react with cold water. Metals like aluminum, iron and zinc do not react either with cold or hot water. Metals such as lead, copper, silver and gold do not react with water at all.
3: There is no reaction between dilute hydrochloric acid or sulfuric acid and the metals below hydrogen in the reactivity series.
4: Yes. The product that forms is called rust.