Is it possible for two different equipotential lines or two lines of force to cross ??
Ha, subtle. A priori, no, you'd think and in general this is correct. However, there can be saddle points and the potential line with the value equal to the potential of the saddle point will show a "crossing".
However, clearly, potential lines with DIFFERENT potential values cannot cross. Idem for field lines (except of course at singularities, like point charges, where they all meet).
If V(x,y) is the (electrostatic) potential, then you can construct an analytic complex function V_c(x+i y) such that Re( V_c(x+i y)) = V(x,y) and Im(V_c(x+i y)) = constant gives you the field lines.
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