Q: If you lose the pathfinder window, how do you open it again?
From the options bar on the top-left of Illustrator (or top-left of the screen on Mac), open "window", then find and click "Pathfinder" to show the window.
Q: Name at least five things the pathfinder can do
Unite — It unites multiple shapes together.
Minus front, Minus back — The minus shape deletes the part of the shape that the minus shape covers.
Intersect shape — Takes the intersection shape of the two overlapping shapes.
Outline — outlines the stroke path of two shapes, then groups the paths together.
Q: If you divide an object, how do you separate the pieces?
If you're using a PC, just use the A-shortcut tool, then move the separate piece. If it doesn't work, just ungroup, then move the piece using the V-tool or the A-tool.