What is the fundamental principle of the Lassaigne test?

Which of the following compounds is not expected to show Lassaigne's test for nitrogen?

Name the methods used for determining the molecular mass of organic compounds.

Given below are two statements :
Statement $I$ : Nitrogen,sulphur,halogen and phosphorus present in an organic compound are detected by Lassaigne's Test.
Statement $II$ : The elements present in the compound are converted from covalent form into ionic form by fusing the compound with Magnesium in Lassaigne's test.
In the light of the above statements,choose the correct answer from the options given below :

The copper wire test for halogens is known as:

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

List-$I$ (Functional group detection)	List-$II$ (Change observed during detection)
$A$. Unsaturation (Baeyer's test)	$I$. Red colour appears
$B$. Alcoholic group (Ceric ammonium nitrate test)	$II$. Silver mirror appears
$C$. Aldehyde group (Tollen's reagent)	$III$. Violet colour appears
$D$. Phenolic group ($FeCl_3$ test)	$IV$. Discharge of pink colour

Choose the correct answer from the options given below: