The fusion of manganese dioxide with $KOH$ in the presence of an oxidizing agent like $KNO_3$ yields a compound. Identify the compound and its color.

Identify correct statements from below:
$A$. The chromate ion is square planar.
$B$. Dichromates are generally prepared from chromates.
$C$. The green manganate ion is diamagnetic.
$D$. Dark green coloured $K_2MnO_4$ disproportionates in a neutral or acidic medium to give permanganate.
$E$. With increasing oxidation number of transition metal,ionic character of the oxides decreases.
Choose the correct answer from the options given below:

Which metal oxide is used to make blue glass?

Which of the following is most basic in nature?

The colour imparted by $Co(II)$ compounds to glass is

In the dichromate dianion $(Cr_2O_7^{2-})$,which of the following statements is correct regarding the $Cr-O$ bonds?