The Middleton test is used for the detection of which element?

For testing halogens in an organic compound with $AgNO_{3}$ solution,sodium extract (Lassaigne's test) is acidified with dilute $HNO_{3}$. What will happen if a student acidifies the extract with dilute $H_{2}SO_{4}$ in place of dilute $HNO_{3}$?

Match column $-I$ and column $-II$ with the correct relation:

Column $-I$	Column $-II$
$(i).$ Lassaigne's test	$(a).$ By sodium peroxide
$(ii).$ Test for nitrogen	$(b).$ Acidify with acetic acid
$(iii).$ Test for sulphur	$(c).$ Acidify with conc. sulphuric acid
$(iv).$ Test for phosphorus	$(d).$ Fusion with sodium

Which of the following substances will give the Lassaigne's test for nitrogen?

Three students,Manish,Ramesh,and Rajni were determining the extra elements present in an organic compound given by their teacher. They prepared the Lassaigne's extract $(L.E.)$ independently by the fusion of the compound with sodium metal. Then they added solid $FeSO_4$ and dilute sulphuric acid to a part of the Lassaigne's extract. Manish and Rajni obtained prussian blue colour,but Ramesh got red colour.
Ramesh repeated the test with the same Lassaigne's extract,but again got red colour only. They were surprised and went to their teacher and told him about their observation. Teacher asked them to think over the reason for this. Can you help them by giving the reason for this observation? Also,write the chemical equations to explain the formation of compounds of different colours.

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