easy way to blur entire background using elements 12?

1. Duplicate the picture layer and add a layer mask to the duplicate.

2. Filter > Blur > Gaussian Blur, and move the slider to get the amount of blur you want.

3. Activate the Brush tool. Set the Foreground/Background color chips at the bottom of toolbar to their default white/black values.

4. Click the layer mask to activate it, and paint black on the picture to restore the focus. If you paint too far, paint with white to restore the blur. You can type "X" to toggle between black and white.

Note: In some cases it might be easier to turn off the visibility of the blurred layer and use the various selection tools to select the foreground subject. Then turn on the visibility of the blur layer and fill the selection with black.  If necessary fine-tune the result using the Brush tool.

No.

Use one of the selection tools to select the foreground, then place it on a separate layer (CTRL+J).

Then, blur the entire picture (Background layer)

You can also do it utilizing a mask. Will be pleased to provide instructions if you desire.