I've installed the 1.1a and 1.2 patches (from Ubi's website, in that order).
These patches are ancient ones from the attic, they're meant for version 1 of the game whereas you have version 4 installed (at least I assume you have, otherwise all your efforts to get UP3 up and running are simply waste of time).
can't find rts.dll
Yep, good old 1.x times. That's due to installing old patches.
What you need to do is to update your game to 4.10.1m first, starting from whatever version you have.
E.g. you have 4.07m, then you need to install 4.08m, 4.09m, 4.10m and then 4.10.1m.
When you did so, install the UP3 base package, then install the UP3 RC4 patch on top.
If you want to make life easier but don't fear huge download packs, you might want to give the "Stock 4.07m to DBW 1.71 SuperPack One-Stop Download & Install (the famous SAS F'nBigSuperPack !)" a try, which installs on any stock game version from 4.07m onwards (which means it's also valid if you already updated to let's say 4.09m) and gets you all you need, including D2D patch, UP3 and it's offline brother "DBW":http://www.sas1946.com/main/index.php/topic,21514.msg239532.html#msg239532
Best regards - Mike