Downgrading from 4.2.1 to 3.1.2

[barrg0]

hotos:Hi all,
I have recently bought an Iphone 3g with version 4.2.1 firmware and 6.15 Baseband, jailbroken and unlocked. I have noticed that it freezes occasionally, is slow to respond and has a very weak Wifi reception range i.e 3-4 metres. I am therefore considering downgrading to 3.1.2. due to the overwhelming thoughts from members that this v4 software is the culprit.
Q. Is this likely to cure these problems I've listed?
Q. I have a Telstra Sim card and need to know which custom ipsw file to use if I go ahead and downgrade. Is it the Activated or Non Activated version?
Q. If I downgrade will I need to unlock the phone again?

Any help would be appreciated.

Cheershone:

 

[Teflon80]

I am currently using a 3G wiv d same version as yours and have that problem sometimes av been told by many that it will cure this problem, only downside is that ur 3G fone when downgraded will not support most of the new apps. An occasional reset always does the trick for me and doesn't freeze that much.