Not the iPad Air, not the iPad Pro. The iPad 2 (iPad2,1 through 2,4) is unique because it uses an older bootrom (the checkm8 vulnerability). This makes it exploitable in ways newer iPads are not.
can skip the activation screen, but the device may lock again if it loses power or restarts. DNS Bypass Ipad 2 9.3.5 Icloud Bypass Untethered
To confirm it is truly untethered:
For the iPad 2 on iOS 9.3.5, the method used dictates which result you get. Not the iPad Air, not the iPad Pro