Identify $A$ and $B$ in the following reaction sequence:
Aniline $\xrightarrow[KCN]{NaNO_2/HCl} (A)$ $\xrightarrow{SnCl_2/HCl/H_3O^+} (B)$

In a reaction of aniline,a coloured product $C$ was obtained as shown below:
$A$ $\xrightarrow{NaNO_2/HCl} B$ $\xrightarrow{N,N-dimethylaniline, \text{cold}} C$
The structure of $C$ would be:

$(i)$ Write structures of different isomeric amines corresponding to the molecular formula,$C_{4}H_{11}N$. $(ii)$ Write $IUPAC$ names of all the isomers. $(iii)$ What type of isomerism is exhibited by different pairs of amines?

Consider the following reaction sequence:
$p$-Nitrotoluene $\xrightarrow{P} Q$ $\xrightarrow{R} S$ $\xrightarrow{H_2O} T$
$S \xrightarrow{U} \text{Benzoic acid}$
Identify the correct statements from the following:
$(A) P = H_2/Pd, \text{ethanol}; R = NaNO_2/HCl; U = 1. H_3PO_2, 2. KMnO_4-KOH, \text{heat}$
$(B) P = Sn/HCl; R = HNO_2; S = p-\text{toluenediazonium chloride}$
$(C) S = p-\text{toluenediazonium chloride}; T = p-\text{cresol}; U = 1. CH_3CH_2OH, 2. KMnO_4-KOH, \text{heat}$
$(D) Q = p-\text{nitrobenzoic acid}; R = H_2/Pd, \text{ethanol}; T = p-\text{cresol}$
Which of the following combinations is correct?

Which set of products will be obtained in the following reactions?
$RCN \xrightarrow{\text{reduction}} (a)$
$RCN \xrightarrow[(ii) H_2O]{(i) CH_3MgBr} (b)$
$RNC \xrightarrow{\text{hydrolysis}} (c)$
$RNH_2 \xrightarrow{HNO_2} (d)$

In the hydrolysis of aniline,the reagent used is: