Suppose, Venus becomes tidally locked. Will its dark side cool enough so that the CO2 from atmosphere to precipitate in liquid form to make an ocean?
While Venus is not tidally locked to the sun, it rotates slow enough that you might as well consider it tidally locked.
However you have to disentangle the slow rotation from the superrotating atmospheric motion. The fast atmospheric rotation (as reaction of the atmospheric gases to the intense solar radiation) redistributes heat very efficiently in the upper atmosphere.
In the lower atmosphere, no significant winds are observed, but the atmosphere has a large density, which through heat conduction again makes redistribution of heat efficient.
All in all, Venus' atmosphere has therefore a horizontally uniform temperature. Said differently, next to no dayside-nightside temperature gradients exist. Nothing will precipitate.
Furthermore the $CO_2$ at the surface is superfluid due to the intense pressure, and this state doesn't seem to form droplets, it IS a sort of highly-viscous $CO_2 $-ocean.