Check option A: Borax bead test for copper

In the borax bead test, copper salts give:

• blue-green bead in oxidising flame
• red/opaque bead in reducing flame due to formation of metallic copper or cuprous oxide.

So statement A is correct.

Check option B: Reaction of $Cu^{2+}$ and $Ni^{2+}$ with $H_2S$ in presence of $HCl$

In qualitative analysis:

• In acidic medium ($HCl$ present), only group II cations precipitate with $H_2S$ because sulfide ion concentration is low.
• $Cu^{2+}$ belongs to group II and gives black precipitate of $CuS$.
• $Ni^{2+}$ belongs to group IV, and it does not precipitate with $H_2S$ in acidic medium. It precipitates as $NiS$ only in alkaline medium.

Therefore the statement that both $Cu^{2+}$ and $Ni^{2+}$ give black precipitate with $H_2S$ in presence of $HCl$ is incorrect.

Check option C: Ferric ion with potassium thiocyanate

$Fe^{3+}$ gives a blood-red complex with thiocyanate ion: $Fe^{3+} + SCN^- \rightarrow [FeSCN]^{2+}$

Hence statement C is correct.

Check option D: $Cu^{2+}$ with potassium ferrocyanide

$Cu^{2+}$ reacts with potassium ferrocyanide, $K_4[Fe(CN)_6]$, to give a chocolate-brown precipitate of copper ferrocyanide.

Therefore statement D is correct.

Conclusion

The only incorrect statement is: $\boxed{B}$