Right, sit down and be quiet you need to pay attention because this is a bit confusing. Marvel vs. Capcom: Infinite is getting a demo, but it’s only available for one weekend. It’s also only available for PlayStation Plus subscribers, and it contains just the versus mode, but you will be able to play against anyone who has either the demo or the full game.
You can play all thirty characters who launched with game in both training mode and online casual matches. The demo will run from December 8th at 12PM GMT until December 11th at 12PM GMT.
I’m not sure why they’ve called it a demo when they could have said “There’s a free trial of the versus mode” and everyone would know exactly what they meant. Silly Capcom.
Source: PS Blog