confirming how to go from 3G 4.2.1 (bb 6.15) to 3.1.3 (bb 6.15)

[Lithowa]

So I am about to embark on the epic quest of downgrading my iPhone 3G 4.2.1 with bb of 6.15 to 3.1.3 with bb 6.15 and I wanted to outline my setups here to make sure I wasn't missing anything.

1. sync iphone with itunes.

2. build a custom firmware 3.1.3 that has 6.15 as the bb with pwnage tools

3. pull out t-mobile sim card and put in at&t one (from and other iphone 3g that is working)

4. shift click in itunes to install the custom firmware.

5. go to jailbreakme.com on the iphone to jailbreak

6. (not clear on this part) put the t-mobile sim back in the phone and use the newest redsnow to unlock bb 6.15

7. sync iphone with itunes to put all the info / apps back onto it.

Will that work?

[Simon]

Do not restore to a custom firmware with 6.15 baseband. You already have that so no need to install it again. Your first steps should be to shift restore to a regular 3.1.3 firmware in itunes. Then use tiny umbrella to exit recovery when you get the 1015 error. Then activate the phone with the ATT sim. Then go to jailbreakme.com. Then install ultrasnow from cydia to unlock.

[Lithowa]

Thank you I will do that.

when i go to restore the iphone itunes gives me the error "the backup "iphone" cannot be restored to this iphone because the software on the iphone is too old. to restore this iphone from this backup you must first set up the iphone as new and restore the software to the latest version." was should i do get get the data back on my phone?

[Simon]

You can use something like iphone backup extractor or juicephone to manually get your data from your last backup.

[Lithowa]

so i have gotten all the data from the backup using iphone backup extractor where do i put it?

[Simon]

You have to manually put each one you want back into your phone with something like iPhonebrowser or ifunbox.