No "full global illumination" option in light path settings in Cycles? I saw the "full global illumination" option once, and I clicked the minus sign there. Now I only have this "Integrator Presets".

Did I accidentally delete "full global illumination"? How can I get it back?

There are surprisingly few Google hits on this.
you accidentally deleted the preset. Just hit the plus sign and set it to the below settings and label it full global illumination.