In the engine bay of my 2015 2.0 there are 3 bolts protruding from the bulkhead, behind the battery. They don't have any nuts on them. Is this normal? I was hoping that this might be the source of the rattle which I hear when driving on poor surfaces.
No, not those. The bolts stick out of the bulkhead seperating the engine bay and the cabin. In your image they would be between your red circle and the hydraulic fluid reservoir.
No they are nothing. The car is available with different engines and transmissions and those studs (they are not bolts) hold various brackets and pipes not on your car.
Is that car one owner? I can't tell by the garbage picture, no point of reference although that does look like part of the battery in the foreground. It's possible those are studs for heatshields that attach to the fire wall, however due to the perspective it's hard to tell.