About dative covalent bonding and expanded octet rule
To answer your first question: the concept of octet expansion for main group metals is no longer generally considered correct and only upheld by the more traditional organic chemists that don’t deal with inorganic bonding situations on a day-to-day basis — or anybody else who didn’t need to recheck what they were taught decades ago. Nowadays, these seemingly octet-expanding structures such as $\ce{XeO4}$ or $\ce{XeF2}$ are explained by dative bonds and/or four-electron-three-centre bonds; both have the beauty of not requiring d orbitals (whose energy would be comparable to the next shell’s s orbital; remember the aufbau principle!).

To answer your second question: no. A dative bond always requires two electrons that are given to one atom upon supply of the bond dissociation energy. It doesn’t matter how a certain bond is created, it only matters how it dissociates; and if it dissociates and was a bond, it will have to have had an electron pair.