When you open Environment Variables first Window.
There is User variables and System variable(has highest priority).
Go also into System variable
And leave all other variable alone in System variable
Restart Pc.
There is User variables and System variable(has highest priority).
Go also into System variable
Path
and make sure that only version poster over is there.And leave all other variable alone in System variable
Path
,delete so only has one Python version as mention.Restart Pc.