#1 - what is the difference between " N " and " DN " ?

Thease are just printer options.

If you don't see any of these, that means just Basic Print option.

" N " - network printer

" D " - Duplex

" DN " - Duplex Network

" C , CL, CLX " - color laser

" MFP " - Multifunction (print, copy, fax, scan)

" F or FN " - Multifunction (print, copy, fax, scan) - usually for Samsung.

" W " - Wireless

" FW " - Multufunction + Wireless