In the Lassaigne's test,the Prussian blue precipitate is formed due to the formation of which compound?

Match List-$I$ with List-$II$.

List-$I$ Element detected	List-$II$ Reagent used/Product formed
$A$. Nitrogen	$I$. $Na_2[Fe(CN)_5NO]$
$B$. Sulphur	$II$. $AgNO_3$
$C$. Phosphorus	$III$. $Fe_4[Fe(CN)_6]_3$
$D$. Halogen	$IV$. $(NH_4)_2MoO_4$

Choose the correct answer from the options given below:

The Lassaigne's extract is boiled with dilute $HNO_3$ before testing for halogens because,

Given below are two statements :
Statement $I :$ In Lassaigne's test,the covalent organic molecules are transformed into ionic compounds.
Statement $II :$ The sodium fusion extract of an organic compound having $N$ and $S$ gives prussian blue colour with $FeSO_4$ and $FeCl_3$.
In the light of the above statements,choose the correct answer from the options given below.

Why is the Lassaigne's extract boiled with concentrated $HNO_3$ before testing for halogens?

Which of the following compounds will give a positive Lassaigne's test for both nitrogen and halogen?