Can't speak for the first part but...
Backroom: depends on time of the day but basically you "pull" product from backroom and send it to salefloor where the flow team will push it to the floor. You will also "backstock" the overstock from the floor and the truck unload process. Dayside backroom has different tasks but the basics are the same.
Flow team: Starts with the unloading and sorting of the truck. Product is then sent to the floor where it is stocked. Some stores seperate backstock straight from the truck some send almost everything to the floor first. Heavily depends on your store volume and process start time. Overnight/third shift, 4am start, 6am start and 7/7:30am.
Reverse logistics: Runs the dock during the day. Deals with venders and deliveries throughout the day. Also processes product returns and product sweep backs. Pretty sweet job to have. No weekends atleast in my area. If you can get this job.