Flexible display substrate, flexible display panel, and display apparatus, and their fabrication methods are provided. In an exemplary flexible display substrate, a motherboard is formed on a rigid substrate that is magnetisable. The motherboard includes a magnetic first flexible substrate and a plurality of flexible display panels on the magnetic first flexible substrate. When the rigid substrate is magnetized, the motherboard is cut to separate the plurality of flexible display panels from each other, followed by demagnetizing the rigid substrate.