Which one of the following salts gives a green-coloured flame when the salt is tested by a $Pt$ wire?

Which pair of cations can be identified by the borax bead test?

Which of the following gives the chromyl chloride test?

The microcosmic salt is

Given below are two statements:
Statement $I$: Colourless cupric metaborate is reduced to cuprous metaborate in a luminous flame.
Statement $II$: Cuprous metaborate is obtained by heating boric anhydride and copper sulphate in a non-luminous flame.
In the light of the above statements,choose the most appropriate answer from the options given below.

Which ion gives a violet-coloured bead in the borax bead test?