Hi guys,
i'd like to ask U if there's a way to check what type of JB my iPhone has..

The main reson of my question is:

i bought iPhone 3GS 3.1.3(iDetector says it's new bootrom) on internet, already jailbroken, aktivated and unlocked..

i don't have oryginal carrier sim ( i'll try to buy some on net but in some time..

As far as i can see it was hacktivated because YouTube was not work untill i installed PushDoctor..

ok let's get straight to the point.
i want to upgrade to iOS4 or 4.0.1 but i don't know if i'll be able to come back to 3.1.3(hacktivated) (SHSH saved on cydia and HDD) if there'll be a need..

help me guys.. if there is a way to figure it out?