Existence of molecule, bonding nature and energy order of molecular orbitals can be explained on the basis of molecular orbital theory as follows

Molecules having zero bond order never exists while molecular having non-zero bond order either exists or expected to exist.
Higher the value of bond order, higher will be its bond strength.
Electrons present in bonding molecular orbital are known as bonding electrons and electrons present on antibonding molecular orbital are known as anti-bonding electrons and half of their difference is known as bond order.
is incorrect. The correct order of energies of molecular orbitals in molecule is