Which of the following represents the decreasing order of reactivity towards reaction with ammonia?

Give the expected product of the following reaction.

Which of the following reactions produce ethyl cyanide $(CH_3 CH_2 CN)$ as a major product?
$1.$ $CH_3 CH_2 CH=NOH \xrightarrow{(CH_3 CO)_2 O} CH_3 CH_2 CN$
$2.$ $CH_3 CH_2 Cl \xrightarrow{\text{Ethanolic } KCN} CH_3 CH_2 CN$
$3.$ $CH_3 CH_2 Cl \xrightarrow{\text{Ethanolic } AgCN} CH_3 CH_2 NC$
$4.$ $CH_3 CH_2 CON(CH_3)_2 \xrightarrow[\text{Pyridine, } 70^{\circ} C]{C_6 H_5 SO_2 Cl} CH_3 CH_2 CN$

Identify the wrong statement from the following.

The major product in the following reaction is

An organic compound having molecular formula $C_2H_6O$ undergoes oxidation with $K_2Cr_2O_7 / H_2SO_4$ to produce $X$ which contains $40\,\%$ carbon,$6.7\,\%$ hydrogen and $53.3\,\%$ oxygen. The molecular formula of the compound $X$ is