What is the $IUPAC$ name of $CH_3CH_2NHCHO$?

The structure $CH_3-C(NH_2)(CH_3)-CH_2-CO-CH_3$ is:

Which of the following represents the azo group?

Give the $IUPAC$ name of the following compound.

Classify the following amines as primary,secondary,or tertiary:
$(i)$ $1-$naphthylamine
$(ii)$ $N,N$-dimethyl$-1-$naphthylamine
$(iii)$ $(C_2H_5)_2CHNH_2$
$(iv)$ $(C_2H_5)_2NH$

What does the molecular formula $C_3H_9N$ represent?