Convert to MULTIPLAYER 4 racing cars [[unity --> iOs]]

Hello, I have a PROTOTYPE game with 4 cars on a single track, and I need it to be multiplayer on iOS and MAC DESKTOP. What I’m looking for is that when the scene starts in Unity3D, each user with their application, the first one enters a room to wait for the others, to wait for the other 3. Once all 4 are ready, each one presses the READY button to start the race. When all 4 are ready, the race starts after 3 seconds, they compete in a straight line, and upon reaching the end, the positions are shown in text… and a button to exit to the main menu. Possibly, the RESPAWN button won’t be used. I will provide the prototype because the controls are different: a slider for steering right or left, one button to accelerate, and another to brake/reverse only. Again, I will provide the fully functional prototype. I offer $75 USD [[payable once it works]]. here link video: https://youtu.be/21v0D-qMiOo