In VR, you often want to interact via virtual hands with virtual objects. Telling the hands how they should hold those objects can be achieved with different strategies. Here is one!
Developing with a multiplatform approach or with just one platform but multiple possible interaction devices, comes with diverse challenges. You will need a solution providing certain compatibility between input devices, modularizing device dependent code, separating it from other game systems, while providing a unified interface to the rest of the application.
You want to VR-ify a game or add 3D stereo, but the original application integrated complex HUD elements? Some issues may come up with the port. But fear not, for some cases there is a workaround.