Which of the following reactions takes place in Lassaigne’s test for the detection of nitrogen present in an organic compound?

When an organic component and sodium metal fuse, the carbon and nitrogen in the organic compound produce sodium cyanide (NaCN), which is soluble in water. It is converted  to sodium ferrocyanide by the adding of sufficient quantity of ferrous sulphate. Prussian blue ferric ferrocyanide precipitate is created when ferric ions produced throughout the procedure combine with ferrocyanide. To determine how much nitrogen is present in an organic product, a test is utilised. With the use of ferrous sulphate and sulfuric acid, sodium fusion extract is cooked. Ferrous sulphate and sodium cyanide combine to generate sodium hexacyanoferrate (II). Some ferrous is heated with sulfuric acid, which causes it to be oxidised into ferric hexacyanoferate (II) which is prussian blue in colour.

$\mathrm{Na}+\mathrm{C}+\mathrm{N}\stackrel{ }{\to \mathrm{NaCN}}$

${\mathrm{FeSO}}_4+6\mathrm{NaCN}\to {\mathrm{Na}}_4\left[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6\right]+{\mathrm{Na}}_2{\mathrm{SO}}_4$

$3{\mathrm{Na}}_4\left[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6\right]+4{\mathrm{FeCl}}_3\to {\mathrm{Fe}}_4[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6{]}_3+12\mathrm{NaCl}$