Which one of the following lanthanides exhibits $+2$ oxidation state with diamagnetic nature? (Given $Z$ for $Nd=60, Yb=70, La=57, Ce=58$)

Most acidic among the given compounds is:

Which of the following statements is $INCORRECT$?

Which of the following is not a consequence of the Lanthanoid contraction?

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?

Which is the last element in the series of the actinoids? Write the electronic configuration of this element. Comment on the possible oxidation state of this element.