Does Pwned DFU mode allow an iPhone 4 to install any version of iOS?
You need those SHSH blobs. I've tried almost anything else available online, without success. Updating to the latest version via restore (without the blobs) is no problem ofcourse.

When you jailbreak your device it will store the SHSH blob on Cydia server, as you can fetch them from their servers with your current device UID if lost.

A SHSH blob is a small piece of data with Apple's signature connected to your device ID.
Since you can only validate iOS versions with your own device ID, there's currently no way to install previous versions without having "your" blob.

Good luck!