is it possible to unlock my 4?

[DJ NiveK]

I have a 4 on 4.0.1 Unlocked on T-Mobile. I wanna update to 4.2 if I could unlock it again. I've read about shsh blobs and stuff like that, but have no idea what to do.

Is it possible to update without updating the baseband? or should I just wait? or is there a way to run 4.2.1 apps on my 4.0.1 phone?

[Cowboy]

Yes you need a custom Ipsw to preserve your baseband

[Stray]

To check if you have shsh's download tinyumbrella and check.
The Firmware Umbrella - TinyUmbrella

[DJ NiveK]

So just download tiny umbrelka after that i can update and still unlock?

[i.Annie]

You can also go to 4.1 if you have SHSHs for it and preserve the baseband simply by running the TSS server in TinyUmbrella and upgrading to 4.1 stock. A custom firmware is doable, but this method avoids using custom fw. But a cfw is not bad either.

[DJ NiveK]

But i still cant run 4.2.1 apps then

[i.Annie]

Well you can't preserve your baseband if you want to go to 4.2.1. It's really complicated to use a custom fw for iPhone 4 to get to 4.2.1, even then your jb will be tethered.