Re: Set the mouse to left handed.
1) If it's possible.
Many "lock down everything" IT departments remove the mouse settings. Happened to me once, when I attended an interview. They had a technical test on a standard RHS mouse PC. I asked for the mouse to be set up left handed, and it took 30 minutes for them to find a tech who could log in as admin to make the change.
2) If it's practical
There's quite a few industry-wide mice that are clearly intended to be held in the right hand. So even changing settings won't help.
FWIW, ever since I started suffering a touch of RSI, I've found I'm ambidextrous when it comes to mousing, so use my left hand now.