OpenBSD live usb ?

It is true that exists an .iso live USB ?

thx in advance !

Just do a normal installation selecting your USB as a destination drive. Nothing special needs to be done. You can use iso installation media if you have DVD/CD drive. Otherwise to boot from a USB use .fs images provided. You can also do PXE boot mass installation and pool installation configurations from a web server. OpenBSD installer is no nonsense fully scriptable shell only installer.