I've been playing VtMB with the (full) 11.3 patch on my old computer. I kept it at that version because it was recommended to always start a new game when changing the patch version.

I'm moving my installation to a new computer and I'm wondering what to do, I can't find the 11.3 online anymore (only the 11.4 and 11.5 versions). Is 11.3 still available somewhere, or is there a way to upgrade from 11.3 to one of the versions available today without breaking my save game?

Or maybe I can transfer some files from my old computer to the new one, thus copying the installation is it was...

UP 11.3 should still be available from The Patches Scrolls.

How do install the latest unofficial patch on the GOG version since it already came with an outdated unofficial patch installed?

Download the full patch from ModDB, Nexus Mods or The Patches Scrolls, run the installer and point it to your game directory.

thanks much appreciated ;)