Which of the following change the colour of the aqueous solution of $FeCl_3$?

When potassium iodide is added to an aqueous solution of potassium ferricyanide,a reversible reaction is observed in which a complex $P$ is formed. In a strong acidic medium,the equilibrium shifts completely towards $P$. Addition of zinc chloride to $P$ in a slightly acidic medium results in a sparingly soluble complex $Q$.
$(1)$ The number of moles of potassium iodide required to produce two moles of $P$ is. . .
$(2)$ The number of zinc ions present in the molecular formula of $Q$ is. . . .
Give the answer for $(1)$ and $(2)$.

Which of the following statements is correct?

The volume (in $mL$) of $0.1 \ M$ $AgNO_3$ required for complete precipitation of chloride ions present in $30 \ mL$ of $0.01 \ M$ solution of $[Cr(H_2O)_5Cl]Cl_2$, as silver chloride is close to

$A$ mixture $X$ of $0.02 \, mol$ of $[Co(NH_3)_5SO_4]Br$ and $0.02 \, mol$ of $[Co(NH_3)_5Br]SO_4$ was prepared in $2 \, L$ of solution:
$1 \, L$ of mixture $X +$ excess of $AgNO_3 \to Y$
$1 \, L$ of mixture $X +$ excess of $BaCl_2 \to Z$
Number of moles of $Y$ and $Z$ respectively are

Some statements are given below $-$
$(a)$ Coordination compounds $[Pt(NH_3)_3(NCS)]$ and $[Pt(NH_3)_3(SCN)]$ are examples of linkage isomerism.
$(b)$ In the coordination compound $K_4[Ni(CN)_4]$, the oxidation state of nickel is zero.
$(c)$ The hybridization, shape and magnetic moment of $K_3[Cu(CN)_4]$ are respectively $dsp^2$, square planar, $1.73 \ B.M.$
$(d)$ $[Cr(NCS)(NH_3)_5][ZnCl_4]$ exhibits only linkage isomerism.