I wanted to revert from Ubuntu to Windows cuz college n stuff. From what i read, The activation key is stored in the motherboard, it's gonna automatically activate. I only have a 4 GB usb and Windows 8 is 4.1 GB (Seriously?). So... Is Single Language lighter? And will i be able to activate it with my regular key?
No, those are not the same. All those special Windows versions (N, Single Langauge) are extra SKUs/Editions and need a special key for each edition. The Single Language edition has the same size like the normal edition. The only difference is that the Single Language edition doesn't allow you to install other language packs to change the UI language.