The complex ion $[Co(en)_2Br_2]^+$ has two optical isomers. Their correct configurations are:

$A$ blue colouration is not obtained when:

$[Ni(CO)_4]$ is diamagnetic. Which of the following statements is correct for this complex?

Based on the provided reaction scheme,choose the incorrect statement:
$1. \text{Metal nitrate} \xrightarrow{\Delta} A + O_2$
$2. \text{Flame test of metal nitrate} \rightarrow \text{Golden Yellow Flame}$
$3. A + \text{Thiourea} \rightarrow \text{Solution } B$
$4. \text{Solution } B + FeCl_3 \rightarrow \text{Blood red colour complex}$

Excess of $aq. NH_3$ can dissolve

For the reaction $K_4[Fe(CN)_6] \xrightarrow{\text{oxidation}} Fe^{3+} + CO_2 + NO_3^-$,which of the following statements is incorrect?