Their are friend codes and you have a friend roster, you press 1 in the lobby to activate it. Your friend code is a 12 digit number.
I'm not really sure what Private Match is myself. I have a feeling it's for inviting people on your friend roster. I mean, you can start one but you are just sitting in the map by yourself, I can't see how anyone would notice you were there unless it appears in your friend roster. If you go to the options screen while in a Private Match there is an option to 'invite friends'.
You have two choices for the crosshair, classic or modern. Classic is the 4 lines, modern replaces them with triangles. They change colour if people are in your sights.
There's other stuff online like streaks, I think I killed 3 in a row without dying myself and that gave me the option of calling an airstrike by pressing left on the d-pad. It brings lots of carnage for the other team, if you get caught in it, the screen is going red and you need to hide for cover.
After a TDM, there is an intermission and a timer of about 30 seconds before the next match and the same players are back in again unless some leave and some join but you see all this on the screen. You can also change your class while you're waiting. It shows you the previous scores next to the players names too.
