Which of the following cations cannot give a borax bead test?

Which of the following statement$(s)$ is (are) correct when a mixture of $NaCl$ and $K_{2}Cr_{2}O_{7}$ is gently warmed with conc. $H_{2}SO_{4}?$

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.

What is the formula of microcosmic salt?

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

While preparing crystals of Mohr's salt,dil. $H_2SO_4$ is added to a mixture of ferrous sulphate and ammonium sulphate,before dissolving this mixture in water,dil. $H_2SO_4$ is added here to: