Would multi person bikes be possible without the invention of the free wheel?
The “free wheel” is a component of the rear hub that engages when you pedal one way, but not the other. This enables you to pedal forward to move the bicycle forward, but when you pedal backwards, the freewheel just spins. Bicycles without freewheels exist, they are known as “fixed gear” bicycles. Fixed gear bicycles are still used today. There is no real reason that a multi-person bicycle could not also be a fixed gear bicycle. So yes, they would be possible.