$(1)$ a metal of A could be slowly dissolved in diluted $HCl$ aqueous solution, forming green solution of $B$; $(2)$ when NaOH was added into the solution of $B,$ green precipitation of $C$ could be obtained; $(3)C$ can not dissolve in excessive NaOH solution, buy with the help of $N{H}_4^{+},C$ could dissolve in the ammonia solution, forming blue solution of $D$; $(4)$ when freshly formed $C$ was treated with a gas of $E,$ the color of $C$ became deeper, finally a dark$-$brown $F$ was formed; $(5)$ when $F$ reacted with $HCl$ solution, green solution and a gas of $E$ were formed; $(6)$ when heated, the gas of $E$ and the metal of A could be transformed into yellow solid of $G.$ Write down the chemical formula of $A-G,$ and the corresponding chemical reaction equations.$($It$\text{'}$s about d$-$block transition metal elements$)$