Which test is used to detect the presence of halogens in an organic compound?

An organic compound $A$ is oxidized with $Na_2O_2$ followed by boiling with $HNO_3$. The resultant solution is then treated with ammonium molybdate to yield a yellow precipitate. Based on the above observation,the element present in the given compound is:

The Beilstein test is used for the detection of:

Given below are two statements:
Statement $I$ : Sulphanilic acid gives esterification test for carboxyl group.
Statement $II$ : Sulphanilic acid gives red colour in Lassaigne's test for extra element detection.
In the light of the above statements,choose the most appropriate answer from the options given below :

In the qualitative test for the identification of the presence of phosphorus,the compound is heated with an oxidizing agent. It is further treated with nitric acid and ammonium molybdate,respectively. The yellow-coloured precipitate obtained is:

Presence of halogen in organic compounds can be detected using