Provided the water is around 75F to 80F and your filter is well cycled and the tank is large enough there is not much you can do. Maybe a water change could help.
Neither, in general lungs are only good for animals that breath air and fins are used for swimming not breathing. In a water environment, oxygen exchange is accomplished using organs called "gills" and fish have gills.
If it is not breathing and the heart isn't pumping DUHHH
I would need more details, but Tetraodon suvatii comes to mind. It is commonly sold as the pig-nose puffer, arrowhead puffer, Mekong puffer, or hog-nose puffer.
Puffer fish will eat fins before anything. lol. they like bloodworm and more carnivorous foods.
Predators that pose a threat to puffer fish in their natural habitat include sharks, dolphins, sea turtles, and some species of larger fish. These predators are attracted to the puffer fish due to their slow swimming speed and defense mechanism of inflating themselves with water or air when threatened.
It has the ability to eat anything it wants, but the chances of it eating one are slim, and if Sharks were to eat a puffer fish it would soon die because of the poison sack.
so its spikes come out to protect it from anything that tries to eat it
Obviously it is unhealthy. Just let it go on with its life and it will die when it needs to.
Usually its anything bigger than it such as us. Or maybe another fish such as a bass. The babies are usually scared of anything and they might puff up.
Good choices would be a pea puffer, spotted puffer, or a figure 8 puffer
Puffer fish swim like any other fish, by using their fins and streamlined body for movement and gills for breathing. The puffer fish only bloats up its body when it is threatened making it difficult to swim but its not like that all the time, in fact the puffer fish is a very good swimmer
puffer fish are ugly