Which of the following complexes does not give a precipitate with $AgNO_3$ solution?

$AgCl$ dissolves in a solution of $NH_3$ but not in water because

$50 \, mL$ of $0.2 \, M$ solution of a compound with empirical formula $CoCl_3 \cdot 4NH_3$ on treatment with excess of $AgNO_{3(aq)}$ yields $1.435 \, g$ of $AgCl$. Ammonia is not removed by treatment with concentrated $H_2SO_4$. The formula of the compound is:

Which one is the most likely structure of $CrCl_3 \cdot 6H_2O$ if $1/3$ of total chlorine of the compound is precipitated by adding $AgNO_3$ to its aqueous solution?

Which complex is formed when an aqueous solution of $NH_3$ is added to a $CuSO_4$ solution,resulting in a deep blue color?

The active substance in Nessler's reagent used for the detection of ammonia is ..........