SST update and ocean coupled problem

I have some questions about WRF.
1.I found that sst cannot update in vortex-following domain even if I set sst_update=1 and follow the steps from user guide,only sst in the outer
domain(D01) can be updated.
2.WRF provides 3D-PWP ocean-coupled model, but I don't find any useful information in user guide.
How do I use this function? Do I need input ocean variables in WPS?

Thanks.

sst_update must be turned off if you run vortex-following case.
For the PWP ocean model, you can set sf_ocean_physics = 2 to activate this scheme. You also need to set ocean_levels, ocean_z, ocean_t, ocean_s. For details, please see README.namelist in WRF/run directory.
I agree that we don't have sufficient information about the PWP in WRF Users Guide. Please refer to the literature if you are interested in this topic. Below are two papers that may help:
Lee, C.-Y., and S. S. Chen, 2014a: Stable boundary layer and its impact on tropical cyclone structure in a coupled atmosphere-ocean model, Mon. Wea. Rev., 142, 1927-1944.
Lee, C.-Y., and S. S. Chen, 2014b: Reply to comments on symmetric and asymmetric structures of hurricane boundary layer in coupled atmosphere-wave-ocean models and observations, J. Atmos. Sci., 71, 2786-2787.

Will you slove this problem(SST cannot update in vortex-following domain) in future version?

No I don't think so. This is because the child domain is allowed to move following the vortex, which makes it hard to know in advance where the child domain will be located during the integration.