@Patricia3116 You can start by asking the potential guest what the purpose of the trip is and who is going to be joining them. But you can ask any questions you like really....the more questions you ask, the more info will be revealed. Note that if a guest is evasive, then that's a red flag.
Even if you don't use instant book, you can require guests to be verified before they can send a request to book,
https://www.airbnb.ca/help/article/272/can-i-require-guests-to-be-verified-before-booking
But be aware that this is in no way a guarantee that a guest is who they say they are, nor something to trust in. I require it as a useful added layer in the guest vetting process. An in person check in and the requirement that any attendant guests will need to show ID at check in is a good idea, which you did. That informed you more thoroughly about what was going on than anything else, didn't it?