Re: farishtay
i read in the hadith that there is a minor shaitan he is in your nafs and there the major shaitan who only appears when there is a shift in the balance of power, for eg when the person is strengthening his faith then he comes to confuse you.
Jinns are also invisible to us but they can be visible to some sensitives that why i posed the topic that certain sensitive groups of people and animals can sense other beings.