A bicycle is a pedal-driven, human-powered vehicle with two wheels attached to a frame. A mode of transport, sometimes used in sports. It's not a toy. Is a car, or a train, a toy?
A toy is an object that is made, especially for a child, to play with; an imitation, especially of something that adults use, e.g. a toy gun. or something, especially a gadget, that is intended to be, or that is thought of as being, for amusement or pleasure rather than practical use.
A bicycle is not especially made for a children to play with, it's not an imitation of something adults use, and it does have an actual practical use. So, it can't really be a toy.
But you could have a toy bicycle.