Average from the filthe problem

Adding to Rupali's excellent reply, don't forget you've always got the History panel which allows you to step back and undo your previous actions (sometimes a little more helpful than blindly hitting Ctrl + Z / Cmd + Z). You can open the History panel by going to Window > History (F10).

Using the History panel while editing (from the Photoshop Elements User Guide)

Also, another reason for always opening the image you want to work with from the Elements Organizer, as the Organizer will allow you to rollback to the original image (via Version Sets) in case you make a unrecoverable mistake when editing the image.

Hi,

Command+F is used to reapply the previous filter.

To remove filter you can use one of following methods- 

1. Choose Edit > Undo (Command+z).

2. Duplicate the layer using cmd + j. Apply average filter. Remove the filter by selecting the layer and clicking the Delete Layer icon in the Layers panel.

Thanks,

Rupali