Broke a finger in 5th grade, had to try to write left-handed while it healed. Caught myself numerous times trying to write backwards, just mirror image, don’t know what was up with that, it was odd. In adulthood, there are a few tasks that work better for me with my left hand, but my right hand predominates.
Sometimes forgers will try to use the opposite hand in making forged documents. However, the brain impulses for handwriting are the same, and a good forensic documents examiner will not be fooled; they can make an identification regardless of the hand used.