Sodium fusion extract of which compound gives Prussian blue colour with $FeSO_4$?

In Lassaigne's extract of an organic compound,both nitrogen and sulphur are present,which gives blood red colour with $Fe^{3+}$ due to the formation of-

Which of the following compounds will give a positive Lassaigne's test for both nitrogen and halogen?

$A$ solution of $m-$chloroaniline,$m-$chlorophenol and $m-$chlorobenzoic acid in ethyl acetate was extracted initially with a saturated solution of $NaHCO_3$ to give fraction $A$. The left over organic phase was extracted with dilute $NaOH$ solution to give fraction $B$. The final organic layer was labelled as fraction $C$. Fractions $A$,$B$ and $C$ contain respectively

Which of the following substances will give the Lassaigne's test for nitrogen?

Lassaigne's test for the detection of nitrogen fails in