Which of the following $f$-block elements exhibits the highest oxidation state?

Observe the following $f$-block elements: $Eu (Z=63)$; $Pu (Z=94)$; $Cf (Z=98)$; $Sm (Z=62)$; $Gd (Z=64)$; $Cm (Z=96)$. How many of the above have half-filled $f$-orbitals in their ground state?

What are the different oxidation states exhibited by the lanthanoids?

Which of the following elements belongs to the actinoids?

Given below are two statements:
Statement $I$: In the Lanthanoids,the formation of $Ce^{+4}$ is favoured by its noble gas configuration.
Statement $II$: $Ce^{+4}$ is a strong oxidant reverting to the common $+3$ state.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which element from the following lanthanoids has a half-filled $f$-orbital in its observed and expected electronic configuration?