What is the product $P$ obtained in the following reaction? $CH_3CH_2Br + AgCN_{(alc)} \rightarrow P$

$C_2H_5I$ $\xrightarrow{\text{alc. } KOH} X$ $\xrightarrow{Br_2} Y$ $\xrightarrow{KCN} Z$; $Z = \dots$

Arrange the following compounds in decreasing order of their reactivity for hydrolysis reaction:
$(I)$ $C_6H_5-CH_2-Br$
$(II)$ $C_6H_5-CH(Br)-C_2H_5$
$(III)$ $CH_3-CH_2-Br$
$(IV)$ $C_6H_5-CH(Br)-C_6H_5$

Which compound gives acetaldehyde upon reaction with aqueous $KOH$?

What is produced when toluene is heated with chlorine in the presence of light and in the absence of a halogen carrier?

The reaction of chloroform with concentrated $HNO_3$ yields ........