How did I just restore a jailbroken Iphone 3g to 3.1.3 using itunes

[6stars6]

Ok shoot me if I am wrong but I thought you could not restore to 3.1.3 just using itunes. I just did it today.

Here is the story....
I jailbroke my 3g with spirit.

I used it for 2 years.

Got an Iphone 4 for Christmas.

I want to sell the 3g so I tried to reset the settings using the feature on the iphone. (Erase all content and setting) Yes Dumb move but I fixed it so far.

After doing that it was stuck on the apple logo boot screen with the pinwheel not moving.

Did some reasearch and decided to use snowbreeze 2.1 to upgrade the ipsw to a custom 4.1 and keep the baseband.

Made the custom ipsw and restored through itunes. looked like it was working but in the end, guess what? it was stuck on the snowbreeze logo. Tried that one more time and did the same thing.

Read on this forum I should try to use snowbreeze 2.0 and try to make a 3.1.3 custom ipsw and try that.

So while I hade snowbreeze 2.0 open making a custom 3.1.3 ipsw I got impatient and I opened itunes and put the 3g into restore mode. Itunes recognized it and I did a (shift) restore selected the stock 3.1.3 ipsw i downloaded from (iPod, iPhone and iPad Firmware Download)

Now I have an Iphone still in 3.1.3 with the same base band as before. (5.12.01)
Its like a new phone again.

Never used the custom 3.1.3 ipsw.

Now the question is, are you supposed to be able to do that? and whats the best way to jailbreak and unlock.

[Simon]

Yes, iPhone 3G doesnt require SHSH for 3.1.3