Which of the following statement(s) is/are true?

Ag⁺ + HCl → AgCl$\downarrow$ + H⁺
The precipitate dissolve in concentrared HCl, AgCl$\downarrow$+ Cl^- + AgCl₂^-
When KCN is added in small amount the Cu²⁺ ions first form a yellow precipitate of Cu(CN)₂ which on standing decomposes to white precipitate of CuCN.
$$\begin{gathered} \begin{array}{r}{\mathrm{Cu}}^{2+}+2{\mathrm{CN}}^{-}\to \mathrm{Cu}(\mathrm{CN}{)}_2\downarrow ;\\ \text{ (yellow ppt.) }\end{array} \\ \underset{\text{ yellow }}{2\mathrm{Cu}(\mathrm{CN}{)}_2}\to \underset{\text{ white }}{2\mathrm{CuCN}\downarrow +(\mathrm{CN}{)}_2;} \\ {\mathrm{Hg}}^{2+}+{\mathrm{Co}}^{2+}+4{\mathrm{SCN}}^{-}\to \underset{(\mathrm{Blue} \mathrm{precipitate})}{\mathrm{Co}\left[\mathrm{Hg}(\mathrm{SCN}{)}_4\right];} \\ \underset{(\mathrm{Black} \mathrm{precipitate})}{{\mathrm{Bil}}_3}\downarrow +{\mathrm{H}}_2\mathrm{O}\to \underset{\mathrm{Orange}}{\mathrm{BiOI}}\downarrow +2{\mathrm{H}}^{+}+2{\mathrm{I}}^{-} \end{gathered}$$