Unreal Engine royalties only start after you make $1 million from a project. Even then, it’s 5%, and waived for sales done on the Epic Store (whose 13% cut is almost a third of what Steam takes). If you are a small indie dev, you won’t be paying Epic a dime unless you start rolling in some serious dough, and even when you do, 5% of your revenue for using one of the most powerful 3D game engines is pretty fair
Without any crime to suspect you of, they might detain you and question you. It’s not uncommon for people to turn themselves in for crimes, and there are legitimate reasons to do so especially with a lawyer, namely to get out on bail easier, avoid having the police raid your home or place of work, and perhaps used to sway the prosecution for a more favorable sentencing, but if the police have no clue what to even charge you for and they can’t figure one out, they’ll just be confused and frustrated, which is a dangerous combination for police