Lassaigne's test for nitrogen is negative for which compound?

In the detection of carbon and hydrogen,the organic compound is heated with which of the following?

Which one of the following sets of elements can be detected using sodium fusion extract?

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:

Nitrogen can be estimated by Kjeldahl's method for which of the following compounds?

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?