if it gets it from another ill cat, or if it gets some sort of disease or illness
The feral cat has either decided to trust you, OR the cat is sick. A cat will often isolate, stay in one place, and even hide when in pain or ill.
Yes, fleas can make a cat ill because the bites can get infected
It is an observation because you can see that the cat is ill so it is visual.
ask your vet
Take it to a vet.
It's an inference because your drawing a conclusion (that the cat must be ill)so it is inferrence
I think it is a inference because you are observing the cat.
It is an inference
If the rat had a disease and the cat eats it, the cat may indeed fall ill. However, a cat's digestive system is perfectly designed to eat raw meat and can easily handle some amount of bacteria. The rat would have to be incredibly sick for a cat to fall ill.
It is an inference
Take it to the vet, that's all you can really do, it might get quite ill !
If the cat is bitten by the millipede while eating it, the cat could become very ill. The cat will need to be taken to a vet for treatment.