Q: Iphone 3Gs 4.1 major update issues to 5.1.1!

The short version- I have a SIM free 3GS phone running on 4.1. I tried to update to 5.1.1 and it crashed completely and i had to take it to a store to repair it back to 4.1 which is fine but now several of the apps that i had dont work, such as ibooks, google earth, IMBD and hipstamatic. Because their new versions require 4.2 or 4.3 etc...

The Question: can I safely update my iphone to at least 4.3 or preferably 5.1?

if not can I find old versions of these apps that will work on 4.1?

The detailed version:

I have an iphone 3GS that has been running wonderfully on 4.1 for a long time.

I had the phone unlocked to make it SIM free.. I dont think it was 'jailbreak' just unlocked.. I do have Cydia app though?

Anyway i never updated the phone from 4.1 because I was worried it would lose the unlock.

I was told by my phone company that i could update without this problem, so I synced and backup up my phone and the pressed 'udpate to 5.1.1' in itunes. It went through the motions. It backuped fine, downloaded software fine, installed software .. then it popped up a message saying the iphone 'cant be updated' and just quit the installation-  leaving the iphone completely wiped! The iphone only showed a symbol saying connect to itunes although it was connected. Itunes said there is no sim in the phone- but there was.

The only option it gave me was to restore to factory setting, so i tried to restore, it reset everything but then when I went through the settings on the iphone- language settings etc, it tried to activate settings/software.. and it said 'this may take up to 3 mins' and then it just stopped and said 'software server is temporarily unavailable please try again later".

I tried several times, eventually I took it to a mobile repair shop and $30 they reinstalled back to 4.1 still SIM free, but without any data on it.. so then I restored/synced with my itunes using 'restore from previous phone settings/backup' and its all fine with all my data exactly as it was except that ibooks and other apps wont upload on to the iphone...

I have tried to delete ibooks app from itunes and from itunes media/mobile applications folder, then copy an old backup version of the app back into itunes, resync with iphone:  but it still wont sync to the iphone.

Also when i try to upload videos to the iphone it wont let me saying they are in the wrong format- is this a different issues?

I REALLY need itunesU and iBooks and would love to have the other apps back too!

how can I get around this issue? I am scared to try and update the iphone again but if i dont then I cant use these and many other apps that are now only for 4.3 and above..

someone please help!!

Thanks!