Trying to unjailbreak IP4 but need to verify that if this will work

[elhomero]

My iPhone 4 4.0.1 JB done with jailbreakme has been acting wonky for a while, I tried uninstalling a lot of the stuff from Cydia but I still get app crashes. So my plan is to upgrade to the latest firmware (4.2 or 4.2.1?) to unjailbreak it then downgrade back to 4.0.1 and just rejailbreak it.

I'm going with this method since I want to preserve my application save data which I would lose during a restore.

If there is anything with my logic here, correct me.

I have saved my SHSH blobs through TinyUmbrella and when I JB'd my phone the "make my life easy" option in Cydia. I also have a file called iPhone3,1_4.0.1_8A306_Restore.ipsw which is supposed to be the 4.0.1 firmware for iPhone 4's.

 

[Chone]

That will work but... why not just jailbreak 4.2.1?

 

[elhomero]

That will work but... why not just jailbreak 4.2.1?

I've been so behind in the JB scene last I heard 4.2.1 for PC users was still tethered while Mac had an untethered option.

Edit: Seems that sn0wbreeze 2.2 is what Windows users can use to JB 4.2.1

 

[Weiser878]

I used TinyUmbrella and upgraded from 4.0.1 to 4.2.1 but kept my 1.59 baseband and then used Greenpois0n to JB and everything worked fine. All my data was saved and texts were still there, etc...

 

[eastercat]

There is an untethered jb for 4.2.1 using green poison.
However, you don't have to upgrade to 4.2.1 then downgrade if your ultimate goal is 4.0.1.
As long as you have the blobs, you can install 4.0.1 with the corresponding blobs and while running the TU server.