Convection carries heat from the mantle to the bottom of the lithosphere. The core is metallic, with the outer layer being molten but the very center being solid due to high pressure. None from 4 billion years ago, so they were erased by other processes. Erosion got rid of most of the craters and changes the Earth's surface in many ways. Mostly due to water, some due to wind.
Erosion is more important on Earth than on the other planets.
Volcanism is important on Earth because it not only created our atmosphere but it also reshapes the surface. Tectonics also shapes our surface, causing ridges, valleys, mountain ranges, etc. Other planets have tectonics going on, but we may be the only one with plate tectonics. 2 million years ago. Plates move at rate of a few centimeters per year.