Which one of the following compounds will give an orange precipitate when treated with $2,4-$dinitrophenylhydrazine?

Which of the following compounds will react with ethanolic $KCN$?

Identify the products $A$,$B$,and $C$ in the following reaction sequence:
$C_6H_5CONH_2$ $\xrightarrow{P_2O_5, \Delta} A$ $\xrightarrow[(ii) H_2O]{(i) DIBAL-H} B$
$A \xrightarrow[(ii) H_3O^+, \Delta]{(i) (CH_3CO)_2O/CH_3COONa} C$

The compound that does not undergo haloform reaction is

When ethanal $(CH_3CHO)$ and propanal $(CH_3CH_2CHO)$ undergo cross-aldol condensation with dilute $NaOH$, the pair of products obtained by cross-condensation reaction is:

The starting material is $CH_3COCH_2CHO$. The reaction sequence is:
$CH_3COCH_2CHO$ $\xrightarrow[{(ii)LiAlH_4}]{{(i)ethylene\,glycol/dry\,HCl}} A$ $\xrightarrow[\Delta ]{H_3O^{+}} B$
What will be $B$?