I don't know if it can go horizontal, but I doubt it. I'd definitely put the solatube on the roof of the garage as it would capture the most light, then you only need to figure out how to get it into the kitchen...perhaps if there is a closet above?

I've been told it would be hard as there are joist and we have to go through the second floor and the attic. I guess no one seemed optimistic.

There should be no problem with the horizontal part--light does not care. The only issue is having enough room to take the corners. Your tube supplier must offer angle pieces to change angles. You must have enough room to go from the roof angle to horizontal at one end and go from horizontal to ceiling angle at the other end of the tube. Total run length and each corner taken increase loss of light.