I love falling in love ... perhaps that's why I've done it so many times. The butterflies, the excitement every time they call, the "can't stop grinning and/or thinking about them" feelings ... it's quite grand.
But while falling in love has been quite easy for me...staying
in love is quite another story. That's the tricky part.
As for the first question, for me, YES. I just knew.
As for the 2nd, it's happened both ways for me. Several boyfriends I met and had that "instantaneous" feeling...not love at first sight, perse, but very intense LUST at first sight that quickly developed into love/lust.
But with several others, the feelings happened slowly over time. With my most recent ex, we were co-workers and friends for at least a year before any romantic feelings developed (at least on my end).
With my current...well let's just say that it took me approximately 16 years to realize that I loved him. It's been well worth the wait, I must say.