Questions about Steam workshop SDK and other multiplayer solutions

Hi folks! I have two questions for you :

  1. Is it possible to use Steam workshop SDK within our UE4 game and to sell it on Epic Games Store? If that’s ok with Epic, is it also ok with Steam?
  2. Knowing that Epic doesn’t have (at least for now) a mutliplayer SDK solution and that our game is fully made with blueprints, could you advice me other party solutions, such as Photon Engine (but this one doesn’t work for us since C++ project is required for this one), please?