Which of the following gives a green colour to flame?

When a metal of group $1$ was dissolved in liquid ammonia,the following observations were obtained :
$(a)$ Blue solution was obtained initially.
$(b)$ On concentrating the solution,the blue colour changed to bronze colour.
How do you account for the blue colour of the solution? Give the name of the product formed on keeping the solution for some time.

In which of the following reactions is hydrogen gas not liberated?

$2Na_2O \overset{400 \ ^oC}{\rightleftharpoons} A + 2Na$
$A + SO_2 \to Na_2SO_4$
$A + CO \to Na_2CO_3$
In the above reaction,$A$ is:

Which of the following combinations will produce $H_2$ gas?

The metal that produces $H_{2}$ with both dil. $HCl$ and $NaOH_{(aq)}$ is