How many isomers of $C_4H_{11}N$ are secondary amines?

What is the major product of the reaction when the given compound undergoes Hofmann exhaustive methylation?

Which reagent,when reacted with a primary amine,evolves nitrogen gas?

The reaction of aniline with excess liquid bromine gives $......$.

What is the final product $C$ in the reaction sequence: $CH_3CH_2NH_2$ $\xrightarrow{HNO_2} A$ $\xrightarrow{PCl_5} B$ $\xrightarrow{NH_3} C$?

$Ph-NH_2$ $\xrightarrow[Br_2]{HNO_2} A$ $\xrightarrow[Warm]{H_2O} B$
$B$ is