Assertion: Aluminum and zinc metal evolve ${\mathrm{H}}_2$ gas from $\mathrm{NaOH}$ solution.
Reason: Several non-metals such as $\mathrm{P},\mathrm{S},\mathrm{Cl}$.etc. convert to hydride instead of producing ${\mathrm{H}}_2$ gas from $\mathrm{NaOH}$..

Aluminum and zinc metal evolve hydrogen gas from sodium hydroxide solution.

$\mathrm{Zn}+2\mathrm{NaOH}\to {\mathrm{Na}}_2{\mathrm{ZnO}}_2+{\mathrm{H}}_2$

$2\mathrm{Al}+2\mathrm{NaOH}+2{\mathrm{H}}_2\mathrm{O}\to 2{\mathrm{NaAlO}}_2+3{\mathrm{H}}_2$

Several nonmetals convert hydride as,

$\begin{array}{l}{\mathrm{P}}_4+3\mathrm{NaOH}+3{\mathrm{H}}_2\mathrm{O}\to 3{\mathrm{NaH}}_2{\mathrm{PO}}_2+{\mathrm{PH}}_3\\ 4\mathrm{S}+6\mathrm{NaOH}\to {\mathrm{Na}}_2{\mathrm{S}}_2{\mathrm{O}}_3+2{\mathrm{Na}}_2\mathrm{S}+3{\mathrm{H}}_2\mathrm{O}\\ {\mathrm{Cl}}_2+2\mathrm{NaOH}\to \mathrm{NaCl}+\mathrm{NaClO}+{\mathrm{H}}_2\mathrm{O}\end{array}$

This reaction of ${\mathrm{Cl}}_2$ is with cold and dilute $\mathrm{NaOH}$.

$3{\mathrm{Cl}}_2+6\mathrm{NaOH}\to 5\mathrm{NaCl}+{\mathrm{NaClO}}_3+3{\mathrm{H}}_2\mathrm{O}$

This reaction of ${\mathrm{Cl}}_2$ is with hot and conc. $\mathrm{NaOH}$.

Both the statements are correct but how aluminum and zinc metal evolve hydrogen gas from sodium hydroxide solution is not explained.

Hence, Assertion: is True, Reason  is True, reason  is NOT a correct explanation for assertion.