A mold fossil is fossil formed when sediment fills the inside or covers the outside of a dead organism and the organism's remains do not persist, leaving just the shape and texture of the rock to indicate the organic material that was there. The difference is Fossil molds and casts preserve a three-dimensional impression of remains buried in sediment. The mineralized impression of the organism left in the sediment is called a mold. The mineralized sediment that fills the mold recreates the shape of the remains. This is called a cast. The thing that they have in common is Fossils also form from molds and casts. If an organism completely dissolves in sedimentary rock, it can leave an impression of its exterior in the rock, called an external mold. If that mold gets filled with other minerals, it becomes a cast. And the last one is your opinion hope this helps!
