Guignet's green is known as

$MnO_2$ when fused with $KOH$ and oxidised in air gives a dark green compound $X$. In acidic solution,$X$ undergoes disproportionation to give an intense purple compound $Y$ and $MnO_2$. The compounds $X$ and $Y$,respectively,are

For $Cu_{2}Cl_{2}$ and $CuCl_{2}$ in aqueous medium,which of the following statements is correct?

$Fe_2Cr_2O_4 + Na_2CO_3 + O_2$ $\xrightarrow{\text{Fusion}} [X]$ $\xrightarrow[H_2O]{H^{+}} [Y]$ $\xrightarrow{H_2O_2/H^{+}} [Z]$
Which of the following statements is true for the compounds $[X]$,$[Y]$,and $[Z]$?

Given below are two statements:
Statement $I$: Fusion of $MnO_2$ with $KOH$ and an oxidising agent gives dark green $K_2MnO_4$.
Statement $II$: Manganate ion on electrolytic oxidation in alkaline medium gives permanganate ion.
In the light of the above statements,choose the correct answer from the options given below.

Compounds of $d-$block elements can stabilize in higher oxidation states only with $F$ and $O$. Which statement is incorrect?