Which statements about the purification of bauxite by the Baeyer process are correct?

1. A$\mathrm{Al}(\mathrm{OH}){}_3$ is directly electrolysed to aluminium after filtration without any heating
2. Bthe solution of $\mathrm{Na}[\mathrm{Al}(\mathrm{OH}){}_4]$ is neutralised with $\mathrm{CO}{}_2$ or seeded with $\mathrm{Al}(\mathrm{OH}){}_3$ to precipitate $\mathrm{Al}(\mathrm{OH}){}_3$
3. Cbauxite is digested with concentrated $\mathrm{NaOH}$ solution at high temperature and pressure
4. D$\mathrm{Fe}{}_2\mathrm{O}{}_3$ stays undissolved and is filtered off