Which of the following statements is incorrect for primary amines?

Write structures of different isomers corresponding to the molecular formula $C_{3}H_{9}N$. Write $IUPAC$ names of the isomers which will liberate nitrogen gas on treatment with nitrous acid.

Consider the following four compounds $I, II, III,$ and $IV$.
Choose the correct statement$(s)$.
$(A)$ The order of basicity is $II > I > III > IV$.
$(B)$ The magnitude of $pK_b$ difference between $I$ and $II$ is more than that between $III$ and $IV$.
$(C)$ Resonance effect is more in $III$ than in $IV$.
$(D)$ Steric effect makes compound $IV$ more basic than $III$.

The decreasing order of basicity for the following amine compounds is:

Compare the basic strengths of the given compounds:

Choose the correct option.