13. Is gapless playback supported by the default player app FiiO Music?

A: Yes, X7, X5III and X7MKII can support Gapless playback, and you can set it through "FiiO Music Settings" ->"Gapless playback" -> On/Off

Notice: The gapless playback feature already added from FW1.0.6 on X5 3rd gen.