Does green poison unlock and jailbreak?

[SAWYER]

I successfully ran Green Poison on a 3gs but I do not have a sim to test if it is actually unlocked. How can I tell? It does have Cydia on it

 

[kaerflog]

Little complicated.
You need to also update the bandband to 06.15.00 to be able to unlock it using ultrasn0w.
I think you need to use redsn0w to update the baseband.

BTW, what version is your 3gs on 4.2.1 ??
And look at the serial number on your 3gs and tell me the first 5 digits.
The 4th and 5th digits tells the week it was made.