Tap the player, then use the CC and audio-note menus to switch tracks. Embedded tracks come from the manifest; sideloaded are external WebVTT files attached by the app. "Multi-audio" carries the film's three real mixes — stereo, Dolby 5.1 surround and the Music & FX track with no dialogue (switch and the voices vanish). "Positioned" attaches a VTT exercising every cue setting (line / position / align / size) — the browser honors authored positioning natively.