In order to play any game on FightCade, you will need to obtain the ROMs for the games you wish to play and go to "Locate ROMs folder" in the Settings menu to tell FightCade where you placed your game ROMs.
You don't need to open any ports on your router: FightCade uses a modern NAT traversal technique that allows to connect two players without having to forward ports, making the setup easier :-)
If the game is supported in the version of FBA bundled with FightCade then yes, otherwise no.
If it is supported and you want it included in the next update, please send us a good savestate file for the game using a pull request or opening an issue to the savestates repository. Make sure the game works fine by playing it in the "Unsupported Games" room first.
At the moment we are using the netcode from GGPONET library, from the original GGPO. As the source code for this library is not available we have to stick with the older version of FBA for now.
We do plan to update FBA to a newer version but this is an involved and time consuming process. If you have experience with netcode, or emulator programming and want to get involved, please contact us.