Which of the following statements are incorrect?

Molecular orbitals of diatomic molecules are designated as σ (sigma), π(pi), δ (delta),etc. In this nomenclature, the sigma (σ) molecular orbitals are symmetrical around the bond-axis while pi (π) molecular orbitals are not symmetrical, e.g. the linear combination of ls orbitals centered on two nuclei produces two molecular orbitals which are symmetrical around the bond axis.