Is there any way to remove all of my previous post from my Facebook timeline? Or remove all activities from a Facebook app with a single click?
There is no first-party way to delete it, but you can set it so that only you can view it.
Head to Privacy Settings and edit the "Who can see my stuff?" setting so that only you can.
Next, use the "Limit The Audience for Old Posts on Your Timeline" tool to retroactively change the privacy setting for every previous post on your timeline.
From now on, only you will see anything that would normally appear on your own timeline.