As I said, most of the requests I get are from seasoned guests with 5* reviews, who send infomative, friendly messages with the request, which make it clear they have read the info, so I really haven’t had to ask many questions.
Occasionally I’ve gotten one of those request messages that just says “Arriving at noon”, so my tactic with those is to answer “Hi XX, thanks for the request. I just want to ensure that you are aware that…” (a couple of things that a guest would have had to read through the info thoroughly to be aware of).
Since I reopened after being closed for Covid, though, I added a vax requirement to my listing, and many guests have neglected to confirm that they are vaxed in their request message. Those are the ones I’ve had to prod, and some of whom have ghosted me, leaving me with a pending request with a ticking time clock. I gave them 12 hours before messaging them again, and if they still didn’t respond after another 4 hours, I considered them non-responsive.
I would never do long term bookings myself through Airbnb, unless it was a repeat guest who I trusted- it seems overwhelming to me to be able to vet a guest, online, who didn’t have lots of glowing 5* reviews. I’ve rented out the entire house in Canada I used to own on year-long leases, but I did that in the usual way, directly, and interviewed prospective renters in person, got references, damage deposits, etc. And most of them still turned out to be less than stellar renters. I wouldn’t want to try to vet guests for long term through an online platform, so I’m not really a good person to give advice on that.
One thing you could do is say on the long term listing that you only accept month-long bookings from guests with at least 5 previous 5* reviews (or ten, whatever). Then if you get a request where you don’t see that, you don’t have to say “I just can’t trust you with my house for a month”, you simply point out that they don’t meet your stated requirement.
Your idea for getting a friend to IB the other listing is clever, but if you did it more than a couple of times, Airbnb might take notice, since the requests would be overridden, but the IBs would then get cancelled right away. It would be a pattern that their algos might pick up. But I’m just guessing on that.