Hi Ashmita,
The clickPast plug-in sets a "click through" event based on the value of a variable and a "click past" event on the following page view. I've never heard of s.firstPage, and looking in our internal wiki doesn't provide much insight either.
Some plug-ins are created by our consulting team to provide additional functionality to your implementation. Chances are the two plug-ins were implemented with the help of one of our consultants a long time ago.