Assuming such a stellar body is even possible, could human or animal life (also assuming they have a way to avoid being pulled toward the planet's core) breathe its outer atmosphere? Would such life be crushed by the atmosphere's pressure?
Jupiter's surface gravity is only 2.4 times that of earth. Uranus is only 0.86 of earth. So gravity is no issue as long as you can stay aloft in the atmosphere.
The level at which the atmosphere is too dense for life depends on the biological machinery of the life in question. The density varies from the top to the bottom of the atmosphere. It is reasonable to say that life cannot exist right at the top where the density is very very low and the radiation is very high, or at the bottom in which the pressure is immense.
Depending on the size of your gas giant, all kinds of things are possible and many science fiction stories feature airborne plants and animals living in the atmosphere of suitable gas giants.
The main thing is being able to reliably maintain altitude within some given band.
A simple search on google will turn up articles like this
May I introduce you to the Ice Giants? The ice giants are formed of sulfur, oxygen and nitrogen with a relatively small amount of hydrogen and helium (20%) compared to Jupiter and Saturn (90%).
200 K is -73C so life as we know it isn't breathing that atmosphere.
Gas giants are no place for life as we know it. Period. Reason being that a gas giant is composed 95% of gas. The core of a gas giant is composed of gas which condensed to liquid/solid form under incredible pressure. At the surface of a gas giant, the pressure would be at horrific levels (earthly life forms would be crushed into less than 50% their earth volume).
Also, since there are no large water bodies on the planet, the heat difference between the day and night sides would be extreme, leading to storms, dunes and vortexes, the magnitude of which reels the brain and makes us shiver in horror. Read about the Giant Red Spot to know what I am talking about here! Forget life. Anything larger than a virus would be torn apart into shreds within seconds.