If a cat is dead it will not move no matter what you do to it and it will not be breathing.
Breathing
If it is not breathing, then you can assume that it is dead.
A cat that has died will not be breathing, moving or responding to you, and depending how long the cat has been dead might be a little stiff from rigor mortis from setting in.
Yes u can get harmful infection.
NO
Breathing in alkali may not be harmful to a person. However, one should avoid breathing any type of alkali in high volumes.
lack of oxygen would be a harmful effect.
Chocolate
yes
Breathing sodium chloride aerosols is recommended to treat asthma.
the cat was breathing rapidly for the dog had scared it.