Which of the following reactions is incorrect?

In the Ostwald process for the manufacture of $HNO_3$,which of the following is used as a catalyst?

Given below are two statements :
Statement $I$: In group $13$, the stability of $+1$ oxidation state increases down the group.
Statement $II$: The atomic size of gallium is greater than that of aluminium.
In the light of the above statements, choose the most appropriate answer from the options given below:

Which oxides of nitrogen are present in significant amounts in the atmosphere?

In which of the following compounds does hydrolysis take place through $S_N^1$ and $S_N^2$ mechanisms respectively?

The elements $N$,$P$,$As$,$Sb$,and $Bi$ belong to which group?