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

${\mathrm{Fe}}^{3+}$ gives red precipitate with dimethyl glyoxime in alkaline solution.

${\mathrm{Cu}}^{2+}$ ion with potassium iodide solution gives a dirty brownish white precipitate which turns white on adding hypo solution.

A filter paper soaked in mercurous nitrate turns black in contact with ammonia gas.

${\mathrm{Ag}}_2\mathrm{O}$ does not dissolve in nitric acid and ammonia solution.