An object is placed far away from all the objects that can exert force on it. A frame of reference is constructed by taking the origin and axes fixed in this object. Will the frame be necessarily inertial?
Since the object is placed far away from all the particles that can exert force on it. Thus, the force on the object is zero, its acceleration with respect to all the other objects will we zero. So, the frame will necessarily be an inertial frame.