The baby balloon was inflated and tied tightly so that the balloon does not let air through.

The baby balloon was inflated and tied tightly so that the balloon does not let air through. After that, the ball was squeezed by hands. How do the following change (increase, decrease or does not change): a) the mass of the gas; b) gas volume; c) gas density; d) the number of gas molecules inside?

According to the definition and laws of physics, gas occupies the entire available volume, then we get the following:
a) if we assume that the ball is absolutely airtight, then the mass will not change
b) the volume of the gas does not change, unless the force with which it will be compressed makes it condense, that is, turn into a liquid
c) the density may change
d) if only the gas does not interact with the surface, then no change.