Trivia

In old versions of the game, all Sonics had the insta-shield except Metal and Super Sonic.

In one version of the game, all Sonics had their own abilities instead of sharing them all.

Amy and Rouge never had a drill move in old versions.

S1 Sonic was the only playable character in Version 1.

You needed the Sonic 2 debug mode code for an incomplete S2 Sonic (most animations were broken) in Version 4.

Green Hill Zone Act 2 was a placeholder with different layouts in older versions until Version 8 were it became the GHZ Act 2 from Sonic 1 with Hill Top's colors.

All Sonics had the same life icons and some characters had a question mark icon in Version 4.

All levels were empty, like now enemies or rings in Version 4.

The only levels in Version 4 were: Test Zone Act 1, Act 2, and Act 3, Green Hill Zone Act 1, Marble Zone Act 1, Emerald Hill Zone Act 1, Chemical Plant Zone Act 1, Casino Night Zone Act 1, Mystic Cave Zone Act 1, Collision Chaos Act 1, Sandopolis Zone Act 1, and House Zone.

The level select was different. Instead of being an S2 title card, it was the options menu from S2 but it's all black.

Most levels had no backgrounds and the spindash had no spindust.

The version for Android was not laggy in Version 8 but in other versions, it's laggy.

Mushroom Hill Zone was added in either Version 5 or Version 6.

Test Zone Act 3 was removed in like Version 5, not sure.

Scrap Brain and Aquatic Ruin were added in Version 6 or 7.

Test Zone Act 2 was turned into Angel Island in around Version 7 or 8.