What is the highest oxidation state exhibited by actinoids?

Fill in the blanks:
$1.$ The atomic radii of the elements of the third transition series are .......... to those of the corresponding elements of the second transition series.
$2.$ Samarium melts at .......... $K$.
$3.$ The color of lanthanoid ions is due to the presence of .......... electrons.

Which elements exhibit nearly identical properties?

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

What are the elements of the $f$-block called?

Fill in the blanks:
$1.$ The size of $M^{3+}$ ions in the actinoid series ........... with an increase in atomic number.
$2.$ The common oxidation state of elements in the actinoid series is .......... .
$3.$ The appearance of elements in the actinoid series is like .......... .