Sorry for my second Post !
I my first i was wrong i actually wanted to know if it is possible to Downgrade from 2.2.1 to 2.0.2 OS Iphone 3 g with Winpwn 2.5 Beta !?
And then to Unlock with Yellowsnow ....
Because right now im up to date with all my basebands and bootloader / OS versions i need to downgrade for Unlocking ... is it right ?

The only way you can downgrade your baseband from 02.30 (2.2.1) is if you are lucky enough to have the 5.08 bootloader on your 3G.

Best way to find out if you have the 5.08 bootloader is to install & run 3G Fuzzyband Downgrader from cydia.

Some Info on Fuzzyband

Fuzzy 3g baseband downgrader. | iPhone News, Help and Guides

BTW
Winpwn doesn't work with 2.2.1 so don't waste your time trying, you need to use Quickpwn or pwnagetool

okey i have the problem right now my bootloader is up to version 6.0 ....
what should be my next step do i have to wait for unlock tool including v.2.2.1 ?

If you have the 6.0 BL & the 02.30 BB sadly you're stuck without an unlock option until hopefully the Dev Team find a solution to make yellowsn0w work with 02.30 BB.

But you could still use Quickpwn225-5 to Activate & jailbreak your phone at 2.2.1 fw 4 now.

iClarified - iPhone - How to Jailbreak Your 2.x.x 3G iPhone Using QuickPwn (Windows)