Which of the following statements is incorrect?

Fill in the blanks:
$(1)$ Since $V_2O_5$ acts as both an acid and a base,it is an ...... oxide.
$(2)$ The $Cr$ oxide which is basic is ......,and the $Cr$ oxide which is amphoteric is ...... .
$(3)$ The formula of chromite ore is .......... .
$(4)$ The formula of sodium dichromate crystal is .......... .

Which mineral among the following contains Vanadium in it?

Which of the following is used in the manufacture of high refractive index optical glass for cameras?

Given below are two statements:
Statement $I$: Fusion of $MnO_2$ with $KOH$ and an oxidising agent gives dark green $K_2MnO_4$.
Statement $II$: Manganate ion on electrolytic oxidation in alkaline medium gives permanganate ion.
In the light of the above statements,choose the correct answer from the options given below.

Which one of the following sulphides is yellow?