If it's tethered, you'd need to install Evasi0n untether for iOS 6 from Cydia to keep it from closing up every time you reboot or turn your device off. As for activating it, since it was previously jailbroken and unlocked using a software unlock, you'll need an original SIM from the original carrier of the iPhone in order to activate it. Otherwise, you'll need to bypass it by removing the setup.app by rooting your device