In Hall-Heroult process for extraction of aluminium (crude) from alumina (Al2O3). Statements (1),(2) and (3) are correct because cryolite (Na3AlF6) is added to Al2O3 to lower, its melting point. Here, steel vessel with lining of carbon acts as cathode and graphite acts as anode, but statement (4) is incorrect because Al gets deposited at cathode.