Which of the following statement or statements is or are correct in case of a source of emf (such as a primary cell)?

Inside the cell there always exist an electrostatic field and a non-electrostatic field of equal magnitude directed opposite to it.

Potential difference is the work of an electrostatic field whereas electromotive force is the work of a non-electrostatic field.

Under certain condition current can flow from positive terminal to negative terminal within the cell.

When an external resistance is connected to the cell, the electrostatic field inside the cell decreases in magnitude compared to the non-electrostatic field.