For the precipitation reaction of $Ag^{\oplus}$ ions with $NaCl,$ which of the following statements is true?

Solubility of $BaF_2$ in a solution of $Ba(NO_3)_2$ will be represented by the concentration term:

Solubility product of a salt $AB$ is $1 \times 10^{-8}$ in a solution in which the concentration of $A^{+}$ ions is $10^{-3} \ M$. The salt will precipitate when the concentration of $B^{-}$ ions is kept

Find the concentration of the ion which is first precipitated at the point when the third ion starts precipitating,if $AgNO_3$ is added gradually to a solution that contains $0.1 \ M \ Cl^{-}$,$0.1 \ M \ Br^{-}$,and $0.1 \ M \ I^{-}$.
Given that:

Salt	$K_{sp}$
$AgCl$	$2 \times 10^{-10}$
$AgBr$	$5 \times 10^{-13}$
$AgI$	$9 \times 10^{-17}$

An aqueous solution contains $SCN^{-}$,$Br^{-}$,$I^{-}$,and $Cl^{-}$ ions. When $AgNO_3$ is added to the solution,which of these will precipitate first? Given: $K_{sp}(AgCl) = 1.2 \times 10^{-10}$,$K_{sp}(AgI) = 1.7 \times 10^{-16}$,$K_{sp}(AgSCN) = 7.1 \times 10^{-7}$,$K_{sp}(AgBr) = 3.5 \times 10^{-13}$.

$H_{2}S$ is passed into $1 \ L$ of a solution containing $0.1 \ mole$ of $Zn^{2+}$ and $0.01 \ mole$ of $Cu^{2+}$ until the sulphide ion concentration reaches $8.1 \times 10^{-19} \ M$. Which one of the following statements is true? $[K_{sp}$ of $ZnS$ and $CuS$ are $3 \times 10^{-22}$ and $8 \times 10^{-36}$ respectively.$]$