Sounds like a nightmare already - be very sure you want to progress as you state you are getting bad signals already from this booking. It's not unusual for a person to have their partner in the photo too - in fact it helps hosts as they see a second face. But in this case the faces are hidden.
There are undoubtedly language issues here, and perhaps cultural ones too.
AirBnB verification is just that - it's verification of a name. It's not a background check. Same goes for passports - they are no different in that all they tell you is the person in front of you has a passport from a specific country (and the name may or may not be correct)
So, summing it up, if I was to be a pessimist, I see this as the basis for your 'Help wanted - non compliant guest and they are here for another 4 months!
On the other hand, persevere and get a face pic uploaded, understand why they are in the same area fo 5 months, etc...