There is a single player AI for both play modes but the AI is not the best at times.
Also I wouldn’t really recommend four players play on a single keyboard. Controllers are definitely recommended. The keys are given below if you would like to try it. It is possible to play with a combination of keyboard and controllers.
Big Birds Racing
7.8
Counter Terror
8.6
360 Smash
7.6
Flappy 3
6.8
Fuzzmon 2 - Mighty Earth
7.6
Battle Robot T-Rex Age
8.1
Dynamons World
8.9
Ancient Fighters
7.1
Dynamons 2
8.7
Friday Night Funkin Vs Hornet
8.1
Agent Pyxel
8.0
Bearsus: Bear Knuckle Fighting
7.5
Fun Volleyball
6.2
Mini Volleyball 3D
8.0
Beach Volley Clash
5.8
Sports Minibattles
6.1
Volley Ball
6.6
Volley Random
7.7
Volleyball Challenge
7.5
Crypto Head Ball
7.3
Volley Bean
6.8
Coconut Volley
8.0
Volley Beans
6.1
Volleyball 2020
6.8
Head Sports! Volleyball
5.6
Extreme Volleyball
6.7
Dino Ball
8.4
Impostor Headball
5.7
Pill Volley Beach
5.3
Volley Squid Gamer
5.2