So here's the thing I've installed The Sims 3 and all Expansions and Stuff Packs including Katy Perry's Sweet Treats, I have no mods/cc installed in the game whatsoever, and I get the modification error, I deleted the caches and still nothing, I mean the game doesn't even load when I click continue, and do not suggest uninstalling and reinstalling because I've already tried that, and I'm getting fed up at this stage :'(

Have you tried to open your game without expansions? just the plain base game? If you have tried uninstalling your game did you use Ccleaner to fix the registry?

If you have had game installed before make sure you don't have any mods still in the old way aka in game folder.
That is one of the known reasons one get the modification error.

Yea I tried that, not working, I'm download the repair utility now to see how that goes.

Nope but I'll try now and see how that goes

Be careful about cleaner programs, though they're most of the times harmless to use for fixing/removing stuff, they can mess up things by removing stuff that shouldn't be touched.
I've learned that the hard way.