I suspect the bigger teams (ie those with a genuine GC contender) can get prepped or even have someone sewing all night to make one
No self respecting TT rider wants to wear a Le Coq skinsuit. They are measurably slower than the kit the riders will have tested in the wind tunnel. Teams have people to make adjustments the night before. In the case of Sky they rebuilt the suit. Sometimes an undergarment has been worn to add aero texture to the yellow skin suit to replicate Endura.
As for frames. Well teams will take a bike frame if they believe it’s a prospect. Normally for the last stage celebration. You won’t tend to see a yellow TT frame. Frames are built up pretty quickly. Bikes can be taped daily anyway. The lead team (hello Movistar) will have their own yellow helmets. And yellow tape for the final.