Hi how do i roll back the game. or download the old version to use lfs tweak or mechanic

I'm not sure if patch P or Q are available on the LFS website anymore, there's certainly not a link in under current downloads or in the archive. You could try searching the various mirrors to see if anyone still has an older copy.

P and Q are still available
just scroll down a bit and u will see it
http://www.liveforspeed.net/?page=archive theres Q
theres P http://www.liveforspeed.net/?page=oldernews