is it a disadvantage if I apply to several universities?

You can apply to five universities through UCAS initially. In the past the universities could see where else you were applying too, however nowadays there is no way that they can tell where else you have applied too. The majority of applicants will apply to 5 universities, as this increases your chance of getting at least one acceptance.

No. Most students apply to multiple universities at once.

When it comes to Cambridge, obviously not everyone gets in, in fact most applicants do not. As such, most applicants also apply to other universities as well, knowing that if they don't get in they'll need a fall-back. Cambridge knows that and expects it.

As it happens, unless a particular applicant was inhumanly good, I'd probably question why they didn't apply to a second university as well.

No, Because Cambridge doesn't know if you are applying to any other University.

Cambridge would not know if you applied to other Universities.

Yes dumaasssss they hate each other