mosfet in as diff device in the before reaching the pinch off region as a voltage dependant resistor due to linear response of the device to the Vds and Id when Vgs<Vp
almost all trannies have some internal capacitance in real time and in off mode they can be used effectively as a capacitor without furthur ip we can't be more helpful
in pinch off region there is a probability of using MOSFET as a constant current source but they need some external biasing for effective usage as current source