I have one hap ax3 on main floor and one Audience on basement and they are connected to each other using ethernet, now I want to create wireless mesh so each time I walk from basement to main floor I don’t need to connect to other SSID, is it possible with my setup?
If both devices are connected to same router using wire (or one of those 2 is acting as router for the complete network), yes.
Simply configure the same SSID on both devices with the exact same security settings.