To find the electric flux at any point inside the metallic sphere of radius \( R \), we need to apply Gauss's Law, which states:
\[
\Phi = \frac{Q_{\text{enc}}}{\epsilon_0}
\]
where \( \Phi \) is the electric flux, \( Q_{\text{enc}} \) is the charge enclosed by the Gaussian surface, and \( \epsilon_0 \) is the permittivity of free space.
For a point inside the metallic sphere of radius \( R \), the Gaussian surface inside the sphere does not enclose any charge. This is because the metallic sphere of radius \( R \) has no charge inside it; the charge \( q \) is distributed on the surface of the sphere.
Thus, the electric flux at any point inside the metallic sphere of radius \( R \) due to the charge \( Q \) on the sphere of radius \( R_4 \) is zero, because the Gaussian surface inside the sphere does not enclose any charge.
Therefore, the electric flux is:
\[
\Phi = 0
\]
Thus, the correct answer is zero.