Upgrade iPhone 4G from iOS 4.1 to any iOS Is there any possibility for me to upgrade to any iOS on my iPhone 4G from iOS 4.1?

Mine is still a nice stable phone, but I can't download any apps. It is jailbroken, unlocked and I have saved the SHSH blobs if that would help.

I have tried updating for a long time, but it did not work because the Apple signing has ceased by the time I try.
You will have to plug your iPhone into a computer and update using iTunes to the latest iOS version. This will of course undo the jailbreak.