This could be false. We don’t know anything about the thickness of any layers of the atmosphere.

This could be false. We don’t know anything about the rate of temperature increase in the stratosphere; it could be the case that the temperature over the equator increases more quickly than the temperature above the poles.

This could be false. We only know the temperature at the point where the troposphere ends and the stratosphere begins; we don’t have enough information to compare points in the middle of the stratosphere.

This must be true. We know that, in the stratosphere, the temperature increases as you go straight up. Because of this, we can infer that any point in the stratosphere is at least as high as the point below it, going all the way down to the highest point of the troposphere.

This could be false. All we know about ozone is that it plays a role in warming the stratosphere; we have no reason to believe that removing something that generates warmth would cause the stratosphere to become warmer.