Examples of B-sides:
Ever free [vogue single] - track 10, no instrumental, no pv, no promotion
Theme of a-nation'03 [& single] - track 4, no instrmental, no pv, no promotion
Two of us [Depend on you single] -track 2, no instrumental, no pv, no promotion
^ all these songs were not included in any albums
Examples of 2nd A-sides:
Game [Inspire single] - track 2, instrumental, pv, promotion
alterna [fairyland single] - track 2, instrumental, pv
is this LOVE? [STEP you / is this LOVE?] - track 2, instrumental, pv, in the title of the single
^ all these songs were included in albums
now.....do you see a pattern? If so, then you know the difference.
