Ethyl amine on heating with $CS_2$ in presence of $HgCl_2$ forms

Which of the following is the most stable species?

Which of the following is the weakest base?

Decarboxylation of all six possible isomers of diaminobenzoic acids $C_6H_3(NH_2)_2COOH$ yields three products $A, B$ and $C$. Three acids give product $A$,two acids give product $B$ and one acid gives product $C$. The melting point of product $C$ is .....$^{\circ} C$.

What is the product formed when acetamide is reacted with $Br_2$ and caustic soda $(NaOH)$?

In the following compounds,the order of basicity is as follows: