HELP ME WITH BIOLOGY PLEASE~ Evaluation & Synthesis?

The aquatic juvenile stage and terrestrial adult stage suggests that it is an amphibian and most likely a frog (Anura). As a juvenile it would need gills for respiration because it lives in the water; think of a tadpole. Obviously since it is aquatic and needs to breathe underwater it is going to have to have gills. The tadpole would probably bring the water in through its mouth and expel it through their operculum. The water and blood go through concurrent exchange so the maximum amount of oxygen get to the blood and max amount of co2 is taken out. Then as they are an adult (frog) they would need a functional lung to breathe in the air. All tetrapods need some kind of lung to breath air, like us, but we use our ribs to produce efficient breathing. Frogs don't use ribs to breathe instead they use a very inefficient way of breathing. As a result frogs also breathe through their skin via diffusion