RE: Tracking by Lot Number
You need to configure each item you want to trackingby lot. On Item Card, you need to set 'Item Tracking Code'. You first need to configure 'Item Tracking Code Card', where and how will be used 'Lot No.'. Since you want to use 'Lot. No.' only to FG, it make sense to set 'Lot Nos.' on Item Card (automatic number series to use for FG). When you set all items you want to tracking, you need to post items with lot no.
If you use only for FG, I will explain posting items with lot no. on Production Order and Sales Order.
In Production Journal, when you fill item quantity for 'Output' entry type, you must to start Lines->Item Tracking Lines. If you use 'Lot Nos.', you need start command Function->Assign Lot No and fill 'Quantity (Base)' field with desired quantity (system fill with all planned quantity). If you work manualy, you must manualy fill 'Lot No.' code and after that quantity. You need to close window and post journal.
In Sales Order, on line where you have item with configured tracking by lot, you need to choose each lot. You must to start Lines->Item Tracking Lines and go drilldown to 'Lot No.' field. You must choose lot no. and fill 'Quantity (Base)' field with desired quantity. You need to close window and post order.
There are a lot of extra functionality, but this is basic for start.