How does the leaving music practical go? Specifically for guitar

How does the unprepared test work? Do you choose one from improvisation, memory and sight reading? For guitar past tests, all I’ve seen were chords written on the paper. Do they just get you to play the chords? In that case, do they care what chord position you use? Do you play along to a track? Any other help/advice about the practical exam would be much appreciated, especially since I’m doing music outside of school.