Which of the following lanthanoids have $[Xe] 4f^x 5d^1 6s^2$ configuration in their ground state? $(x = 1-14)$

The element having electronic configuration $ns^2(n-1)d^{1-10}(n-2)f^{1-14}$ belongs to:

Identify the rare earth element from the following.

Which elements exhibit nearly identical properties?

The chemistry of the actinoid elements is not so smooth as that of the lanthanoids. Justify this statement by giving some examples from the oxidation states of these elements.

All those elements belong to $f-$block whose atomic numbers are