Consider the octahedral cation $[\mathrm{Co}(\mathrm{en}){}_2\mathrm{Cl}{}_2]{}^{+}$ and the related ions. Which statements are correct? One or more options may be correct.

1. Atrans-$[\mathrm{Co}(\mathrm{en}){}_2\mathrm{Cl}{}_2]{}^{+}$ is optically inactive because it has a plane of symmetry.
2. BThe cation has three stereoisomers in total.
3. Ccis-$[\mathrm{Co}(\mathrm{en}){}_2\mathrm{Cl}{}_2]{}^{+}$ is optically inactive because its two $\mathrm{Cl}{}^{-}$ ligands are identical.
4. DReplacing the two $\mathrm{Cl}{}^{-}$ by a third en gives $[\mathrm{Co}(\mathrm{en}){}_3]{}^{3+}$, which has two stereoisomers.