Lithium shows diagonal relationship with

Which of the following statements is incorrect?

Which of the alkali metals has the lowest melting point?

The commercial production of sodium carbonate is done by

The blue colour of the solution (metal dissolved in liquid ammonia) is due to

What happens when : $(i)$ sodium metal is dropped in water? $(ii)$ sodium metal is heated in free supply of air? $(iii)$ sodium peroxide dissolves in water?