still it does mean that CO2 is polar in a sense.
Just like how aldehydes have dipole moments and ketones do as well and they are polar because of that CO2 is polar in a sense because of its quadrupole moment.
No, it doesn't. In chemistry the conventional meaning of "polar" means a dipole moment ≠ 0. Most molecules that don't have a permanent dipole will have some higher order charge distribution like octupole, quadrupole, etc. Calling these "polar" as well would pretty much make every molecule inclusive in the definition, so it would be useless as a general term. Carbon dioxide does not have a permanent dipole moment; that is a fact. Therefore it is considered by chemists to be a nonpolar molecule, irrespective of the polarity of any single constituent bond. This is the accepted definition of "nonpolar".
Why else would CO2-O-C=O be possible other than the fact that CO2 has partially negative oxygens and a quadrupole moment with 0 dipole moment.(in that molecule I wrote the CO2 looks like this [O-C=O O=C-O])
Quadrupolarity has nothing to do with it, first of all. Second, just because molecules are nonpolar does not mean they are nonreactive. You are confusing a lot of different concepts. The polarity of a molecule refers to the overall dipole moment. Individual bonds may be polarized in a nonpolar molecule. But this has already been explained to you. Furthermore, molecules (and their constituent electrons) are not frozen in time. Though carbon dioxide has no permanent dipole moment on average, vibrations can give rise to temporary dipole moments (one C=O bond lengthening, one shortening, say) which are often a gateway toward chemical reactions. Instantaneous fluctuations in electron density and nearby permanent dipoles also give rise to momentary charge asymmetries, even in nonpolar molecules - and these fluctuations are the basis of various intermolecular interactions like London and van der Waals forces. This is why a nonpolar molecule like hexane is a liquid at room temperature instead of a gas.