(4)

Change in potential energy in electric field,

$\Delta U=pE(\cos {\theta }_1-\cos {\theta }_2)$

         $=pE\left[\cos \right(0°)-\cos (60°\left)\right]$

$\therefore$   $\Delta U=\frac{pE}{2}=\frac{5\times {10}^{-6}\times 4\times {10}^5}{2}$

          $\Delta U=1$ J

(3)

Electric field is always direct from high potential to low potential. For the given situation the electric potential is decreasing from left to right therefore, potential energy of the dipole will also decrease. Thus dipole will move from towards the right.