When soldering components on both sides of a board, there's a risk that soldering one side of the board will cause solder joints on the other side to melt.
Manufacturers making PCBAs will approach these by also adding a drop of epoxy to the components on one side of the board, so that they have another adhesive to prevent them from falling off during the soldering process.
The MIRROR command in EAGLE will flip pads/traces/parts to the other side of the board (e.g. in a 2-layer board scenario)
You can export the BOM for a circuit by using "bom" ULP (by using "run bom") from the schematic view.
ULP = User Language Programs. In EAGLE, these can be accessed by typing "run <insert ULP name>" into the command bar. EAGLE has premade ULPs, but users can also program their own.