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

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 :

Which test is useful for the detection of halogens in organic compounds?

During the detection of phosphorus in an organic compound,which of the following is formed to produce a yellow color?

Presence of halogen in organic compounds can be detected using

The violet color obtained in the Lassaigne's test for a sulfur-containing compound is due to the formation of which species?