I'd know in fact if this is possible to get back from the 1.85 to 1.83 ver. I've downloaded the game without modifying my update.dat cause I've get the all game + expention + update in one time. Now I'm playing on Uthgard, they warn us it would be better to play with the 1.83 due to certain bugs that could happen while playing the game. Any of you could help me with this trouble?
(I've look on some website/forum without finding any soluction at all).

Thanks furthermore, Mazh

No, unfortunately, this is not possible. However, as long as you don't plan on starting a big crafting career (currently not working correctly with >1.83) you shouldn't have any issues playing even with 1.85.

Copy the whole game from someone who still has 1.83 is the only solution i can think about.

I started playing here about a week ago and downloaded the US 14 day trial from here:
http://www.darkageofcamelot.com/download/

This installs directly as v1.83 (don't use the online updater!).
After installing the ToA expansion you'll get 1.81, so don't use it.
Catacombs upgrade is v1.83 again. I haven't tested the Darkness
Rising upgrade; only downloaded it but from the timestamp on the
file it seems to be v1.83 too.

Direct download links:
http://mythic.fileburst.com/downloads/DAoC_14-Day_Trial_Setup.exe (about 2GB)
http://mythic.fileburst.com/downloads/trial_to_catacombs_setup.exe (~1.2 GB)
http://mythic.fileburst.com/downloads/catacombs_to_darkness_setup.exe (~0.9 GB)

(i hope providing direct links is ok on this forum)

Good luck