i have 3gs 32gb that it was jailbroken and unlocked with 3.0. then i tried to ERASE ALL CONTENT AND SETTING ( because a lot of info i don't want), BUT I stupidly stopped in middle of process. Then it's stuck in apple logo, tried to upgrade to 3.0.1, redsn0w 8.0, blackra1n, but no either of them works. it can't reboot by using blackra1n, and can't activate by using redsn0w.

CAN ANY ONE ME ADVISE MEAND WALK ME THROUGH TO FIX MY ISSUE? I REALLY APPRECIATE.

The simplest way out of your problem is to restore with a pwnagetool custom ipsw for 3.1 or 3.1.2

Do under any circumstances NOT restore using the official Apple 3.1 or 3.1.2 you will lose your unlock.

If you really want to stay on 3.0.x you have a very slim chance of being able to restore to a 3.0.x if you can retrieve an ECID SHSH for your model.

First, very importantly did you click "make my life easier" in Cydia? Do you know if you have saved your ECID SHSH on Cydia's server,

If you are unsure about whether you saved your ECID SHSH you should try the firmware umbrella.
http://www.hackint0sh.org/f203/87785.htm This is a command line tool that can be used to retrieve ECID SHSH bundles personalized for your phone.

Once you know you have an ECID SHSH for 3.0 or less likely 3.0.1 then you need to change your hosts file to point iTunes restore process at Cydia's server instead of Apple's. How to Downgrade iPhone 3GS OS 3.1 to 3.0 With Cydia SHSH | iPhone This guide will show you how to change the hosts file and do the restore.

really appreciate for your respond. i don't have mac book for first option, and about UMBRELA FIRMWARE, I DON'T THINK THAT I HAVE THAT CHANCE EITHER because i can't go activate my phone, and i don't also want to update to 3.1 or 3.1.2.

To use firmware umbrella, you need the ecid of your phone. Search the forum on how to get that ecid. Once you have it, use umbrella and point it to saurik/cydia server to see if you have the fw 3.0 ecid/shsh hash. If you do, you can restore to fw 3.0.

If you do not have fw 3.0 ecid/shsh then your only way to get that phone going again is to use custom firmware 3.1 / 3.1.2. Since your phone was jailbroken, it has trace of being pwned therefore restore using custom firmware will work.

What ever you do, do not, do not restore with original apple firmware 3.1/3.1.2 because you will loose the ability to unlock.

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Just to clarify, you can easily get your ECID even though your iPhone won't boot. I think that is what you were concerned about.

To get your ECID, put your iPhone into recovery mode.

Make sure the iPhone is not connected to the computer via USB cable.
shut it down (hold down power/sleep and home buttons until the phone shuts down)
Hold down the home button and plug the iPhone into the computer, keep holding the iPhone until it says connect to itunes on the screen. This is recovery mode.

Ignore iTunes offering to restore the phone.

Using usbview on Windows (be sure to enable Config Descriptors) or System Profiler on Mac and read your phones ECID. It's the 16 digits of number/letters after "ECID:"

Umbrella has a GUI and is pretty straightforward to use.

To exit recovery mode hold down both power/sleep and home buttons for around 30 seconds until the iPhone restarts then let them go.

i used custom firmware 3.1.2 with mac (borrow from my friend). get my 3gs back to life. really appreciate you both.