What is the electronic configuration of $Ce$ $(Z = 58)$?

Consider the following statements:
$I$. $La(OH)_3$ is the least basic among hydroxides of lanthanides.
$II$. $Zr^{4+}$ and $Hf^{4+}$ possess almost the same ionic radii.
$III$. $Ce^{4+}$ can act as an oxidizing agent.
Which of the above is/are true?

The correct order of ionic radii of $Ce$,$La$,$Pm$ and $Yb$ in $+3$ oxidation state is

Amongst the given elements,which one exhibits a $+4$ oxidation state in an aqueous medium?

Cerium $(Z = 58)$ is an important member of the lanthanoids. Which of the following statements about cerium is incorrect?

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