I am ambidextrous, but was pushed to be right-handed in first grade. I can do most things with either hand, but didn't pursue writing with my left until I was an adult. I used to be able to play (strum) a 6-string guitar either left or right, but learned to play right-handed. In my early years I was totally ambi, with a slight preference for the left. Now, I write righty, throw righty (although I can throw lefty too, sometimes with better accuracy), but I bat lefty, kick with my left foot, and if I played golf, I would need lefty clubs. I can eat with either hand, with equal dexterity.
One strange thing that I noticed when trying to write lefty was that it was easier to write backwards, with my left hand. My handwriting lefty is nearly identical to my handwriting righty, when you view the lefty writing in a mirror. It seems more natural to make the letters backwards with my left hand.
The bass player who play Paul in 1964 (Beatles Tribute band) is a righty who learned to play lefty for his part in the band. I saw them years ago when they called themselves Revolver, and he played righty then. Now he's lefty, like Paul. He not only plays lefty, but his hand movements and look are very close to Paul's.
I like the old saying that says that left-handed people are the only ones who are in their right mind....