(N/A) $(i)$ Compound $(X)$ does not give the Fehling test,which indicates it is not an aliphatic aldehyde; it is likely benzaldehyde.
$(ii)$ Compound $(X)$ gives the silver mirror test,confirming the presence of an aldehyde group. Combining $(i)$ and $(ii)$,we conclude $(X)$ is benzaldehyde.
$(iii)$ The formation of orange precipitates of benzaldehyde $2,4-$dinitrophenylhydrazone with $2,4-DNP$ confirms that $(X)$ is benzaldehyde.
Chemical Reactions:
$(i)$ Reaction with Tollen's reagent (Silver mirror test):
$C_6H_5CHO + 2[Ag(NH_3)_2]^+ + 3OH^{-} \longrightarrow C_6H_5COO^{-} + 2Ag(s) + 4NH_3 + 2H_2O$
$(ii)$ Reaction with $2,4-DNP$:
$C_6H_5CHO + (NO_2)_2C_6H_3NHNH_2 \xrightarrow{H^+} C_6H_5CH=NNHC_6H_3(NO_2)_2 + H_2O$