How to make Mac's mouse icon to be left hand friendly?
You can use the following app called Mousecape:

https://github.com/alexzielenski/Mousecape/releases/tag/0.0.5

After downloading, installing both the app and the helper app, do the following:


Go to the Mousecape preferences and choose “I am left handed”.
Dump the system cursors into a cape from the menu: “Capes” → “Dump
Cursors”
Apply the Cursor Dump cape (right click → apply)


Done!