I've had an iPhone for 3 years, but I've never jailbroken mine. So I have no idea how it looks like when it is jailbroken. If I'm buying someone's used iPhone, how can I tell that it's not jailbroken? Because if it's jailbroken, they can probably unlock it, but that unlock will only be temporary... I want to avoid that. Also, if they say it's factory unlocked iPhone, how can I verify that? Is the only way to insert two different SIM cards and make sure it works with both, or is there an easier way?