Questions about modding the entire game

So, I want to convert the game to C++ instead of Blueprints, and I’m curious about the ability to distribute the newly designed game. I am working on a project to modify a bunch of the key elements of Robo Recall to port it to another platform, so I don’t want to get into legal trouble if I can avoid it. What assets would I be allowed to freely distribute or modify? I figure this question has been asked, but I couldn’t find the answer specific to my question…thanks