Did a large terrestrial planet ever form in the region of the asteroid belt?
Current thinking is that the Asteroid Belt never constituted a single terrestrial body in the past; for whatever reason, there was not enough mass in the Belt for the matter there to accrete into a single body, as happened in the case of Earth or Mars, e.g.
Ceres is a dwarf planet and it is registered in the minor planet center as asteroid number 1. However, it is a dwarf planet not an asteroid. Asteroids and comets are similar bodies that do not have hydrostatic equilibrium and are relatively small. Recent rulings by the International Astronomical Union (IAU) have reclassified it and justly so (though I personally don't believe dwarf planets and normal terrestrial planets are as different as they contend).
Between the orbit of Mars and Jupiter, there is the asteroid belt. This is made up of millions of small rocks that are in a direct orbit around the sun. Most of these objects are boulder sized or smaller, but some are quite large. The largest is a Dwarf planet called Ceres, which is around 975km in diameter. Its the only one in the asteroid belt called a dwarf planet as it it big enough…
No planet has an asteroid belt on it. The asteroid belt is it's own entity in the solar system. Saturn has a large ring system made of rocks and ice. All the other gas planets have far less extensive ring systems than Saturn. Perhaps that is what you mean. ITS CERES <--No, Ceres in a minor planet inside the asteroid belt.