iOS 5 Restore

Hi,
I have iOS 5.0.1 installed on my iPhone 3GS and I want to restore it, I have already downloaded iOS 5 and I don’t want to download iOS 5.0.1 ( I downloaded it from my iPhone about 40 mb) because I have a slow limited internet connection
I tried to do a shift-Restore but it showed „The iPhone „myiPhone“ could not be restored. This device isn't eligible for the requested build“
What does this mean? Do I have to download 5.0.1? Is there a way to restore 5?

Thanks in advanced

My understanding is that once you upgrade, you can't go back unless you completely wipe the iPhone.

chas_m said:

My understanding is that once you upgrade, you can't go back unless you completely wipe the iPhone.

Click to expand...

What do you mean by „Wipe“
If it will make me able to go back I don’t care caz I will choose to restore the info from my backups, can’t I?

Did you connect your iPhone to your computer, open iTunes, select your iPhone from side bar, and choose "Restore To Factory Settings" from main screen?

MYmacROX said:

Did you connect your iPhone to your computer, open iTunes, select your iPhone from side bar, and choose "Restore To Factory Settings" from main screen?

Click to expand...

Will that affect my SMS and apps data?

And if it did will I be able to restore them?

Kax said:

Will that affect my SMS and apps data?

Click to expand...

Possibly.

And if it did will I be able to restore them?

Click to expand...

I can't answer this authoritatively, but I don't believe iTunes backs that sort of info up. So the answer in that case would be no.

Thank you,
But i guess I will wait for 5.1

It's not just that. The iOS devices check back with the mother ship to see if your device is eligible for a given build (upgrade or downgrade) If your device is eligible then the restore will go on - if it isn't then you get some message about not being eligible for the build. It isn't just a downgrade thing. There is a window that Apple says - you can use this build. It is mainly to thwart jailbreaking - but there are security reasons for it as well.

For example I tried to upgrade my iPad to 4.3.3 from 4.3 - but 5.0 was out and the window to go to 4.3.3 was closed. 4.3.3 had a pdf exploit that could be used to jailbreak the device (but it was also a general security hole that needed patching) - Point is it isn't just a downgrade - it is any build has a window allowed by Apple to be loaded.

More on SHSH blobs
SHSH blob - Wikipedia, the free encyclopedia
Info on SHSH blobs and why it matters to jailbreakers
Cydia Is Now Saving SHSH Blobs For iOS 5.0.1 Firmware | Redmond Pie