Here's what you do for simple solution. Use pin behavior to an INVISIBLE circle and pin on the VISIBLE circle and give rotate behavior too. Give it an image point (1) for your point A. You could also create a small invisible object and pin it to image point(1) and have it represent point A.
When Sprite reaches point A, Pin it, activate rotation.
Also, create an invisible object to represent point B.
When Sprite is "on collision" or "on overlap" with point B. Kill rotate and un-pin sprite and add any other event you need.
Much easier than radius calculations.