On adding $KI$ to a solution of copper sulphate,what happens?

Which is the most reactive metal among the given options?

The copper $(II)$ halide which does not exist is:

Identify the correct order of oxidizing power.

For the four successive transition elements $(Cr, Mn, Fe, \text{ and } Co)$,the stability of $+2$ oxidation state will be in which of the following order?
(Atomic numbers: $Cr = 24, Mn = 25, Fe = 26, Co = 27$)

Discuss the chemical properties of lanthanoids.