What is the coordination number of $Cs^{+}$ and $Cl^{-}$ ions in the $CsCl$ structure?

Which of the following statements is not true about the $NaCl$ structure?

The radius of the largest sphere which fits properly at the centre of the edge of a body-centered cubic $(BCC)$ unit cell is (Edge length is represented by $a$) (in $a$)

How many formula units are there in the unit cell of sodium chloride $(NaCl)$?

The edge length of a face-centered cubic unit cell of an ionic substance is $508 \ pm$. If the radius of the cation is $110 \ pm$, what is the radius of the anion in $pm$?

For $bcc$ cubic coordination the value of radius ratio is