Inversion - to use or not to use...

1) I knew not only...
2) Not only did I know...
3) Not only I knew...

Whould someone be so kind to tell me whether the third example is correct and if there are some other usages of the phrase "not only" at the begining of the sentence?

Thanks in advice,
Flubber ;)

jezeli juz mowimy o inwersji, to tylko zdanie 2 jest poprawne

Moze być tak :

I not only knew, but ( I also ) ...( correlative in meaning similar to ‘just as....so’)
Not only did I know , but I also... ( sub-op inversion, more ‘dramatic’ effect)
Not only I knew , others knew it too ( no inversion when the focus is on the subject )