How can I downgrade my iOS from 4.2 to 4.01?

How to downgrade iOS 5 to iOS 4.3.3? I have search alot but didn't find any workable solution.?

• Recently I have purchase iPhone 3G S (used) with iOS 4.3.3 installed and having 6.15.0 baseband. The device was Jailbreak and UNLOCK with Ultrasnow. Device was working perfectly without any problem. 15 Days back I connect my device to iTUNES and it said there is an update available (iOS 5) and i click update and install. after restart some times my iphone ask me some questions for reconfiguring my device and stucked at activation because it was not supposed to be factory unlocked and need any official sim. My sad story start from here i search a lot and i think i have read the whole internet but only able to jailbreak my device without unlocking. My sim is not working on it now and the only wifi connectivity is available. Location service is also not working, now battery problem is worst it came back from 100% to 10% within few hours and whenever i use my device it becomes hot from the back side. Now i just wanted to pull back my device to iOS 4.3.3 BUT IT IS NOT POSSIBLE THROUGH ANY TUTORIAL AVAILABLE IN THE FIRST 20 GOOGLE SEARCH PAGE RESULTS. I have changed numerous version of iTunes (upgrade or downgrade) but restore stuck some where with different error messages. If any one here to solve my problem?

• Answer:

  06.15.00 is the iPad baseband which there is no going back from.... Pretty sure I can take you through it all... but 1st step is to clarify what iOS are you currently running? Can you go onto Settings----General ------ About and double check?