How many secondary amines are possible with the molecular formula $C_4H_{11}N$?

Which of the following amines, when heated with ethanolic $KOH$ and chloroform $(CHCl_3)$, does $NOT$ produce a foul smell?

Identify the substrate '$A$' in the following reaction: $A \xrightarrow[ii) \Delta]{i) \text{Moist } Ag_2O} CH_3CH_2N(CH_3)_2 + CH_2 = CH_2 + H_2O$

The end product of the reactions is
$C_2H_5NH_2$ $\xrightarrow{HNO_2} A$ $\xrightarrow{PCl_5} B$ $\xrightarrow{NH_3} C$

$R-NH_2 \to R-NH-CH_3$ (major product). The correct sequence of reagents is:

Consider the molecule $1,3-dimethyl-1,2,3,4-tetrahydroquinoxaline$ with an amino group at the $5$-position. Upon protonation,which nitrogen atom is the most basic and will be protonated first? Identify the correct structure of the product '$A$' formed after protonation.