The question about unrelated adults isn't small talk. A standard landlord policy, often a DP3 form, is generally underwritten around a single household occupying the dwelling. When each bedroom is leased separately to unrelated people, some carriers treat the risk as a rooming or boarding occupancy, which either gets priced higher, gets written on a different form, or gets declined. Which of those happens depends on the carrier and on your state, so the practical step is to describe the occupancy accurately, in writing, and have a broker who handles investment property shop it. What you must not do is buy a policy for a single-family rental and let the carrier assume one family, because a claim is exactly when the occupancy gets examined.
Separately, require each tenant to carry renters insurance and name it in the room lease. Their belongings aren't covered by your policy, and with four adults sharing a kitchen the odds of one of them causing damage to another one's things is not trivial.
On the registration form, city rental programs vary widely, and some count dwelling units while others count rented rooms or beds. Email the licensing office with your address and the sentence "I intend to lease four bedrooms under four separate leases," and keep the reply. That email is worth more than anything you'll piece together from the website.
The thing that catches people after the insurance is sorted is the zoning side, which is a different office entirely. Whether four unrelated adults may occupy a single-family dwelling depends on how your local code defines family and household, and how that applies to your property is a question for a local land use attorney rather than for your insurance agent.
