A snake breathes through its nose, since they have lungs. Even fully aquatic species need to come up for air.
Yes.
into the skin
Yes, out of its nose or mouth.
oxygen trransfer
Yes, snakes need oxygen from the air just like any other land animal.
No, a snakes skin is impervious to air. Snakes breath using lungs which are inside their bodies with nostrils at the front of their heads.
All sea snakes must rise to the surface to breathe occasionally, although some can remain underwater for long periods by absorbing oxygen from swallowed water.
Snakes do not breathe carbon dioxide; instead, they inhale oxygen and exhale carbon dioxide like most other animals. Snakes use their lungs to exchange gases during respiration.
One of the main differences is in their skin. Snakes have scales which overlap and are connected to each other by small pieces of skin, while amphibians have a uniform layer of semi-permeable skin though which they can absorb oxygen. Amphibians have eye-lids but snakes don't
All kinds of fish and squids. Also, some sea snakes.
of course all reptiles have blood their just cold blooded
All except for aquatic mammals such as dolphins and whales and reptiles such as snakes and turtles.