The transition element ( $\approx 5 \%$ ) present with lanthanoid metal in misch metal is

State the general electronic configuration of lanthanoids. Why are there irregularities in the electronic configuration of lanthanoids?

The lanthanoid that does $NOT$ show $+4$ oxidation state is

Given below are two statements:
Statement $I$: $CeO_{2}$ can be used for the oxidation of aldehydes and ketones.
Statement $II$: Aqueous solution of $EuSO_{4}$ is a strong reducing agent.
In the light of the above statements,choose the correct answer from the options given below:

What is the correct order of ionic radii for the $+3$ oxidation state in $Ce, La, Pm,$ and $Yb$?

Name the members of the lanthanoid series which exhibit $+4$ oxidation state and those which exhibit $+2$ oxidation state. Try to correlate this type of behavior with the electronic configurations of these elements.