DLC 9S ARENA, Usable robots ?

Hi,

i would like to get all the robot playable. Did anyone know the full list of playable robot in this mode ?
I've already get a lot, but i still have empty slot, and not sure if i have everything (like every game play for the some that i have)

Please help.

I didn't find the right solution from the Internet.

References
steamcommunity.com/app/524220/discussions/0/1520386297689279365/
Startup Explainer Video

Thanks