Which of the following exhibits only $+3$ oxidation state?

Which lanthanoid from the following exhibits $f^{14}$ configuration in the $+3$ oxidation state?

Mischmetal is an alloy consisting mainly of

Although $+3$ oxidation state is most common in lanthanoids, cerium still shows $+4$ oxidation state because:

The correct basicity order of the following lanthanide ions 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: