Fluorine is a poor leaving group (ie has a much higher lieing sigma* orbital). NF3 has vacant orbitals, but they aren't sufficiently low lieing for the hydroxide anion to displace it. In the case of CCl4, the chlorine atoms are rather bulky so you can consider it somewhat like doing an SN2 reaction on t-butyl chloride. The antibonding orbital is present, but its difficult for the hydroxide anion to access it to the steric bulk of the substituents. In the case of CHCl3, if you react it with hydroxide you won't get nucleophilic substitution but rather will see deprotonation to form trichloromethide (CCl3-).
Every element and compound has vacant orbitals. Though we don't ever consider that hydrogen say has d orbitals, it does, they are just of such a high energy that they don't matter to the chemistry. Those orbitals have to exist because we can see them in the emission spectrum of hydrogen when you excite it and the electron relaxes to the ground state.