saranam, i think your question should be better placed in Finite Element Analysis engineering (forum727). This forum is dedicated to FEA theoretical aspect.
Btw, you are right that shell and plate is different regarding DOFs, and hence also the forces acting on it. Shell can accept Membrane forces + Bending Moments, where plate only Bending Moments. The shape of plate is normally plan (straight), thereagainst shell could be curved. SO if an egg skin should be modelled with shell elements.
The comparison between plate and shell is most like bar and beam, right?
regards