Almost, but not always. The final file version (1.05 or 1.06) is identical in content, but Steam uses a slightly different encryption wrapper. Never mix patch files from different storefronts. Always verify via the platform’s own tool.
Reverting to the original patch.dat/fat instantly removes all modded content. Far cry 3 original patch.dat patch.fat download
However, if a mod causes a crash or you simply want to return to the vanilla experience, you might realize you forgot to back up the originals. Here is everything you need to know about restoring these files. Where are these files located? Almost, but not always