Arrange the following in increasing order of ionic radii: $O^{2-}, Na^{+}, F^{-}, Mg^{2+}$

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$:
Assertion $A$: The ionic radii of $O^{2-}$ and $Mg^{2+}$ are same.
Reason $R$: Both $O^{2-}$ and $Mg^{2+}$ are isoelectronic species.
In the light of the above statements,choose the correct answer from the options given below:

The largest difference in atomic radii is found in the case of which pair?

In which of the following pairs are both species isoelectronic,but the first one is larger in size than the second?

Which ion has the greatest radius among the following?

From the given set of species,point out the species from each set having the least atomic/ionic radius:
$(A)$ $F^{-}, Na^{+}, Mg^{+2}$
$(B)$ $Ni, Cu, Zn$
$(C)$ $N^{-3}, Cs^{+}, H^{-}$
$(D)$ $Li, Li^{+}, Be^{+2}$