Questions 1 and 2 are biology, not physics. We can put upper bounds on the physical effects of something, but it is up to biologists to determine if that is harmful to the organism. These questions are also marginally on-topic for at least one technical site and definitely on-topic for the local site for general skeptical inquiries.
Questions 3 and 4 can be made on-topic here, but they should be separate questions. 3 should be phrased in a way to ask about conceptually how microwaves heat living (i.e. water-rich, organic) material. 4 should ask about whether such frequencies are focused by the eye (note that the vitreous humor is at least as important as the lens proper in humans, the former being essentially water as far as physics is concerned, the latter a crystal in some sense).
Again, it is not for physics to say what the harm is, unless you provide the biology necessary for that judgment. For example, if you give a correspondence between electrons ejected from DNA and cancer rate, a physicist can tell you something like "sitting next to a cell tower will cause XXX excess displaced electrons per DNA strand per day due to thermal motions."
I make no guarantees though that these questions have not been asked already. You should check those linked questions in the comments.