Which transition metal compound is used in a dry battery cell?

When potassium permanganate $(KMnO_4)$ is heated at $513 \ K$,it decomposes to form two manganese-based products. The physical properties of the product in which manganese has a higher oxidation state than the other are:

Give the preparation of potassium dichromate and state its uses.
Give the structures of chromate and dichromate ions. How can chromates and dichromates be interconverted?
Give the chemical reactions showing the oxidizing nature of potassium dichromate.

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

$K_2Cr_2O_7$ on heating with aqueous $NaOH$ gives:

Among the following,the compound that is both paramagnetic and coloured is