Going back to this here. I was doing a bit more research and came up with this little Atari 800 personal computer game called Snokie: https://www.youtube.com/watch?v=czFFKT5MA_0
Snokie was released in 1983 and featured non-forced scrolling. I don;t think it had arbitrary scrolling though that moved the screen up/ down and backwards, by the look of it the game only scrolled forward. But this game does have most of the conventions of a standard platformer.
This game was also released on the C64 as well: https://www.youtube.com/watch?v=Pju5Znpy1Vs
Excellent work. Added.