No one of even slight importance recognises Crimea as being Russian, no one outside of the usual Russian bootlickers is going to recognise any of these territories.
How does Russia plan to retain them? By being part of Russia they can send in regular conscripts that are part of Russia's mandatory military service. Since outside of an official war they are not allowed to be deployed outside of Russia. So instead of declaring war to commit them, Putin is simply moving Russia.
Will that work? I doubt it. No matter where they are drawn from, they will freeze the same in winter until a HIMARS strike will, briefly, warm them up.