Which one of the following lanthanide ions does not exhibit paramagnetism?

Write the electronic configurations of the elements with the atomic numbers $61$,$91$,$101$ and $109$.

Provide the electronic configurations of lanthanoids $(4f)$ series elements $(Ln)$ and their ions $Ln^{2+}$ and $Ln^{3+}$,and state their characteristics.

Larger number of oxidation states are exhibited by the actinoids than those by the lanthanoids,the main reason being

The lanthanide ion having four unpaired electrons is
(Given : Atomic number of $Ce = 58, Nd = 60, Tb = 65$ and $Ho = 67$)

Most basic hydroxide among the following is