All Students preparing for Grade exams are recommended to use the Hofnotes on-line training pages to practise for the aural tests.
At higher grades you must be able to discuss with the examiner musical features such as texture, form, style, and period of a piece of music. My own web pages to help with these parts of the test at Grade 5+ and at GCSE are available here!
Music based on major and minor scales came into common usage in the early 1600s, and of course we have been using them ever since. In the Western world, babies start hearing them in the womb, and will be thoroughly acclimatised to scale-based music in infancy. Folk tunes and nursery rhymes see to that!
But before the 1600s, composers wrote in modes. Modes went underground for a while but re-emerged in jazz and the music of Debussy and Vaughan Williams.
For more on scales, including the circle of fifths, see this page.
For scale fingerings, see this page.
For information on chords, see this page.
For information on intervals, see this page.
For information on harmony, see this page.