The incorrect statement is:

• A

  ${\mathrm{Cu}}^{2+}$ ion gives chocolate coloured precipitate with potassium ferrocyanide solution
• Correct answer
  B

  ${\mathrm{Cu}}^{2+}\mathrm{ }\mathrm{and}\mathrm{ }{\mathrm{Ni}}^{2+}$ ions give black precipitate with ${\mathrm{H}}_2\mathrm{S}$ in presence of HCl solution
• C

  Ferric ion gives blood red colour with potassium thiocyanate
• D

  ${\mathrm{Cu}}^{2+}$ salts give red coloured borax bead test in reducing flame

Hence, the correct answer is option: 'B'.