Silver (With A Counter move with a cost of Power) and Metal Sonic

2/3 of them are references to

Sonic's Concept and is also a Skin in Sonic Superstars Cream's Debut (Though inconsistent looks)

A former 90s rival's (A red capped plumber guy) recent 3D platformer since 2017

(coming some time soon or something.) The 1st Sonic Battle Redux arcade Run: Sonic.

The "Big Green Man" (Guest) teaser.

That Hover Move.

It's like the OG game but less stiff.

Where it all began. With A Classic Cameo. Also Silver

Act Music as Rounds? (may not apply to every stage)

Sumin didnt just make some characters But also sandbag (Though bare bones)

(Silver Update)

Another Trap attack + A returning move from Infinite Battle + And another intro

Despite being Water (Or Mutated Chao) slime sounds