Beachballs and almost unresponsive after Sierra upgrade
Just as a sample, it took 1 min to write that question title because after 2-3 keystrokes, the beachball would show up.
With the Yosemite upgrade my MacBook Pro was OK but after El Capitan I started noticing the slowness but it was still ok.
Now with Sierra upgrade, my MacBook Pro (mid-2012) has become completely unusable. A spinning beachball now shows up after just 3 key strokes, 3-5 seconds before the menu opens on right click, even watching a video now is an impossible task.
How do i fix? Is there a way to find the OS X installer and go back to to an older OS version like Mavericks or Yosemite? Or any other suggestion?
The etrecheck report is given below. Any advice or suggestion will be highly welcome.