When borax is heated with cobalt oxide,which of the following compounds produces a blue-colored bead?

In the scheme given below,$X$ and $Y$,respectively,are:
$\text{Metal halide} \xrightarrow{\text{aq. NaOH}} \text{White precipitate } (P) + \text{Filtrate } (Q)$
$P \xrightarrow[\text{heat}]{\text{aq. } H_2SO_4, PbO_2 (\text{excess})} X (\text{a coloured species in solution})$
$Q$ $\xrightarrow[\text{warm}]{\text{MnO(OH)}_2, \text{Conc. } H_2SO_4} Y (\text{gives blue-coloration with KI-starch paper})$

Which of the following is most basic in nature?

Which of the following statement$(s)$ is/are correct?

The most basic hydroxide among the following is

The green colour produced in the borax bead test of a chromium$(III)$ salt is due to formation of . . . . . . :