Statement 1 is correct. PSLV (Polar Satellite Launch Vehicle) is primarily used to launch Earth observation/monitoring satellites, while GSLV (Geosynchronous Satellite Launch Vehicle) is designed to launch communication satellites into geosynchronous transfer orbits.

Statement 2 is incorrect. Satellites launched by PSLV are typically placed in polar or sun-synchronous orbits, which are not geosynchronous. These satellites appear to move across the sky as viewed from a particular location on Earth.

Statement 3 is incorrect. The GSLV Mk III is a three-stage launch vehicle, not a four-stage one. The first stage uses solid rocket motors, the second stage uses liquid rocket engines, and the third stage uses a cryogenic rocket engine.