Several newbie 3gs jailbreak questions

[opus001]

I've been reading up on this jailbreak but I'm confused. I have a 3GS with 4.2.1, but the 4h and 5th numbers in the serial number are 20. That suggests an older version that could handle an untethered jailbreak yet every other indicator says I have to do tethered. So I guess my question is, can I do untethered or not? Is it possible that someone upgraded my phone in a way that prevents me from doing untethered? (I bought this on ebay)

It looks like I'll need to upgrade the baseband to the iPad baseband to get this to work. If I do that, I won't be able to go backwards right? Any advice here?

I bought this phone on eBay to take to Israel which is why I need the jailbreak and unlock. Is there a simple way? I see these websites that want $29 but it seems like they'll just take my money and point me to the same tools that everyone else is using. Correct? Anyone have experience with these jailbreaking sites?

I know this post is a bit random, but I could use some advice.

Thanks.

 

[opus001]

What's the best firmware version to downgrade to if I want to be able to jailbreak and unlock a 3GS running 4.2.1. I want to go to an untethered jailbreak that can be restored via iTunes if I ever need to. 4.1? 4.0.2?

Thanks.

 

[myzhi]

iH8sn0w.com | Jailbreak your iPod touches and iPhones

You can download and run forecast to see if you have old or new bootrom. If old bootrom, 3GS 4.2.1 JB will be untethered.

And, to downgrade to an older firmware, you need to have saved old SHSH files for the firmware you wish to downgrade to. Without them, you can only restore / install the latest firmware, 4.2.1. If you do have old saved SHSH files and new bootrom, 4.1 or below will allow you to have an untethered JB.

 

[opus001]

Thanks so much for the help.

So I did it and here it is (attached). It says unlockable = no. Any idea why that is? I need to use this phone overseas so does that mean I'm out of luck?

What method of jailbreak and then unlock would you recommend? Would I have to update the baseband to the new iPad baseband?

I have no blobs so I guess I can't downgrade to 4.1. Several websites say you can download without blobs, but I'm guessing that might not be true.

 

[myzhi]

It means your 5.15 baseband can't be unlock. Thus, if you want to unlock, you will need to go hack Ipad 6.15 baseband route. Before doing that, you should read up and be fully aware of the issues in doing that.

Since it says "Untethered Yes," means you have the old bootrom, and thus, you can use Redsnow for untethered 4.2.1 JB.

And, YES, you can't downgrade w/o saved old SHSH files. Site that says otherwise are wrong.

 

[opus001]

Thanks again. So bottom line is I can jailbreak untethered and I won't have to mess with hooking it up to a computer on every reboot. Right?

Then once I JB and I can go the iPad baseband route which will allow me to unlock and use with any sim, BUT I can never go back to another baseband below 6.15...meaning I could miss some critical update in the future. The phone would still work though. Right?

If I go the 6.15 baseband route, could I still apply and update to, let's say iOS 4.3 when it comes out? I'm assuming I could since my phone would essentially be like an iPad.

Thanks so much.

 

[myzhi]

Yes, untethered JB means you can reboot the phone like normal. Tethered is when you need to connect to a computer.

And, to update or restore, you must use a custom firmware file. Thus, when 4.3 comes out, you will need a 4.3 custom firmware file to update.