Which oxidation state is common for lanthanoid elements?

Which lanthanoid from the following exhibits $f^{14}$ configuration in the $+3$ oxidation state?

The lanthanoid that does $NOT$ show $+4$ oxidation state is

Which elements exhibit nearly identical properties?

State the $E^o$ values of lanthanoids and provide their reactions with the following: $(i)$ $H_2$,$(ii)$ Carbon,$(iii)$ Dilute acid,$(iv)$ Halogens,$(v)$ $O_2$,and $(vi)$ $H_2O$.

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