Reflections at a boundary

When an incident pulse reaches the ring, the pulse exerts an upward force on the ring accelerating it upward. Since the ring is light, it moves faster than if it were just a segment of the string and the ring moves beyond the height of the incident pulse. The tension in the string exerts a downward force on the ring causing it to come back down. The motion of the ring generates a reflected pulse that has the same amplitude as the incident pulse and is not inverted.
Since the reflected and incident pulses have the same displacement at the free end, the free end has the maximum displacement and there is always antinode at the free end of the string. Reflection at free ends is called soft reflection.

The string end is fastened to a light ring that is free to slide without friction along the rod

When an incident pulse reaches the wall, the pulse exerts a force on the wall. By Newton's third law, the wall exerts an equal and opposite force on the string. This reaction force generates a pulse which is inverted and travels back along the string. The reflected pulse has the same amplitude as that of the incident pulse.
Since the end of the string is fixed, the reflected and the incident pulses must have opposite displacements at the fixed end so as to cancel each other at that point. There is always a node at the fixed end. Reflection from a fixed end is called hard reflection.