Identify the incorrect order corresponding to the mentioned property.

The statement that is not correct for the periodic classification of elements is

$A, B$,and $C$ are hydroxy-compounds of the elements $X, Y$,and $Z$ respectively. $X, Y$,and $Z$ are in the same period of the periodic table. $A$ gives an aqueous solution of $pH < 7$. $B$ reacts with both strong acids and strong alkalis. $C$ gives an aqueous solution which is strongly alkaline.
Which of the following statements is / are true?
$I$: The three elements are metals.
$II$: The electronegativities decrease from $X$ to $Y$ to $Z$.
$III$: The atomic radius decreases in the order $X, Y$,and $Z$.
$IV$: $X, Y$,and $Z$ could be phosphorus,aluminium,and sodium respectively.

Which of the following order$(s)$ is/are correct?
$(1) Li < Be < B < C$ $(IE_1)$
$(2) Li < Na < K < Rb < Cs$ (Reducing power in gaseous state)
$(3) Li^{+} < Na^{+} < K^{+} < Rb^{+} < Cs^{+}$ (Ionic mobility in aqueous solution)
$(4) S > Se > Te > O$ $(EA)$

Nitrogen has positive electron gain enthalpy whereas oxygen has negative. However,oxygen has lower ionisation enthalpy than nitrogen. Explain.

In which of the following sets,elements are not correctly arranged with the property shown in brackets?