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

Another returning move For Amy Rose Amy Flash.

Akin to MUGENhunter's Tails

(Not finalized yet but its a resemblance.) I have decided to make it 3 Buttoned. Though the Basic attacks mapped A,B and C buttons will also be mapped to X,Y and Z

Despite being Water (Or Mutated Chao) slime sounds

Another mechanic that I coded for the first time

"Grab Canceling"

The only thing that varies between character is: how long will they actually throw the opponent while Pressing Y + Holding FWD/Pressing Z + Holding Backwards will still do the cancel trick

I'm taking you down like its 1998/1999!

A returning move from Infinite Battle

but a bit more on Sonic 06's Green Gem.

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

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