Question

Potential inside the sperical shell is

Answer 1

The potential is defined relative to the infinity - not relative to the center of the shell. Since there is no field inside the shell, the potential at any point inside the shell is equal to the potential on the surface of the shell, V=Q4πϵ0.

Answer 2

Inside the sphere, the field is zero, therefore, no work needs to be done to move the charge inside the sphere and, therefore, the potential there does not change.

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