1) name the file “splashscreen.png,” place it in /etc, and change the path in splashscreen.plist to “/etc/splashscreen.png.”
2) I haven’t actually tested this myself, but assume the following works: edit retroarch.cfg and uncomment the following:
input_enable_hotkey = (select)
input_save_state = (right trigger)
input_enable_hotkey = (select)
input_load_state = (left trigger)
3) to set up page up/page down and skip to letter, try
cd .emulationstation
sudo rm es_input.cfg
When you reenter emulation station, it should prompt you to configure your controller.
4) I just use the Genesis emulator for SMS. In es_systems.cfg, I copied the “COMMAND” line from the Genesis section and pasted it in the SMS section (removing or commenting out the existing “COMMAND” line. This works well but the emulator does not support Game Gear.
Hope this helps!