Which of the following compounds will not give a positive Lassaigne's test for nitrogen?

Give the answers for the Lassaigne test:
$(i)$ If nitrogen and sulphur are both present,what observation is observed?
$(ii)$ If bromine is present,what is the observation?
$(iii)$ In the Lassaigne extract,if black precipitates are not obtained upon adding $CH_3COOH$ and lead acetate,what does this indicate?
$(iv)$ What is the reason for adding $FeSO_4$ to the Lassaigne extract?
$(v)$ Why is the Prussian blue colour observed?
$(vi)$ What does the violet colour with sodium nitroprusside in the Lassaigne extract indicate?

Discuss the chemistry of Lassaigne's test.

The volume of nitrogen is measured by which apparatus in the Dumas method?

During the detection of phosphorus in an organic compound,a yellow precipitate is formed due to the formation of:

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