The elements with atomic numbers $101$ and $104$ belong to,respectively

Which of the following statements are correct?
$I$. $P$ has the least negative electron gain enthalpy among $P, S, Cl$, and $F$.
$II$. In $Eu$ and $Yb$, lanthanoid contraction is not observed.
$III$. $Ce(OH)_3$ is the most basic among lanthanoid hydroxides.
$IV$. The radii of $Na$ and $Na^+$ are $95 \ pm$ and $186 \ pm$ respectively.

Which pair of ions among the following can be separated by the precipitation method?

Which of the following properties of lanthanoids is $NOT$ true?

Which is the correct order of ionic sizes $(At. \, No. : Ce = 58, Sn = 50, Yb = 70, Lu = 71)$?

Which of the following statements is not correct regarding lanthanoids?