1. Yes. Additionally, you can make use of TNet's serialization without using any of the networking features (so this can be used as a save system for a singleplayer game, I think).
2. Yes.
3. Yes, but you build the server browser (the GUI part). The data is made available from the lobby server (aka master server).
4. No? Matchmaking in general is very dependent on game logic. How would TNet know what criteria you want for matchmaking? It would be very easy to implement though, as TNet is provided as source code.
5. You must purchase a license for each programmer that contributes to your project. I think you can buy a studio license, too, though. Not sure.
TNet isn't a "click these buttons to make your game multiplayer" type of solution, so expect to do a fair bit of coding. The tutorials, documentation, and the wonderful quality of ArenMook's work makes this a very simple task, though.