Between $Mg$ and $Mg^{2+}$,which has a smaller size? Why?

The statement$(s)$ that are correct about the species $O^{2-}$,$F^{-}$,$Na^{+}$,and $Mg^{2+}$.
$(A)$ All are isoelectronic
$(B)$ All have the same nuclear charge
$(C)$ $O^{2-}$ has the largest ionic radii
$(D)$ $Mg^{2+}$ has the smallest ionic radii
Choose the most appropriate answer from the options given below :

The ionic sizes decrease in the order :-

In which of the following pairs,the difference between the covalent radii of the two metals is maximum?

Which element from the following has the largest atomic size compared to the other three?

Which of the following arrangements represents the increasing order (smallest to largest) of ionic radii of the given species $O^{2-}, S^{2-}, N^{3-}, P^{3-}$?