(i) Both involve electrostatic forces of attraction
(ii) Both are non-directional.
Differences: Ionic bond is a strong bond due to electrostatic forces of attraction while metallic bond may be weak or strong depending upon the kernels.
(b) Unit cell of NaCl has fcc arrangement of $Cl^−$ ions and $Na^+$ ions are present at the edge centres and one at the body-centre.
Thus there are $14Cl^−$ ions and $13Na^+$ ions in the unit cell. However their net contribution towards the unit cell is $4Na^+$ and $4Cl^−$ ions.
(c)Yes because its repetition in different directions produces the complete space lattice.
(d) Ionic solids are hard because there are strong electrostatic forces of attraction. However they are brittle because the bond is non-directional.