The metal that gives hydrogen gas upon treatment with both the acid...

(i) $Mg + HCl \to MgC{l}_{2} + {H}_{2} ↑ Mg + NaOH \to {\left(OH\right)}_{2} + Na$
(ii) $Fe + HCl \to Fe{Cl}_{3} + {H}_{2} ↑ Fe + 2{OH}^{-} \to Fe{\left(OH\right)}_{2} + 2Na$
(iii) $Zn$ is amphoteric in nature, so it reacts with acid as well as base.
$Zn + HCl \to ZnC{l}_{2} + \dfrac{1}{2}{H}_{2}\left(g\right) ↑ Zn + NaOH \to {ZnO}_{2}^{- 2} + {H}_{2}\left(g\right) ↑$
(iv)
$Hg + NaOH \to Hg + HgO + {H}_{2}OHg + 2HCl \to H{g}_{2}C{l}_{2} + {H}_{2} ( g )$