Yes. The whole one-click pipeline is registered as a single undo step, so Ctrl+Z reverts all five stages together.

Quick Mirror adds the modifier with Clipping enabled around the object's local origin. Set the origin (see Origin in the Documentation) to where you want the mirror plane to sit before adding the modifier.

Rename Selected renames every object in the current selection in selection order. If an object doesn't appear where expected, check whether it was deselected (e.g. by clicking in an empty area) before running the operator.

Check the Angle value in Transforms & Shading, a very low angle keeps most edges hard. Also confirm the object didn't have Auto Smooth previously disabled at the mesh-data level on very old files; re-running the operator will re-apply it.