Splitting multi-part polygon into single polygons using ArcGIS Desktop?

Under "Advanced Editing" there is a Button for "Explode Multi-Part features". Worked just fine!

You can use the Multipart To Singlepart (Data Management) tool which:

Creates a feature class containing singlepart features generated by separating multipart input features.

ArcMap, arctoolbox -> data management -> features -> Multipart to singlepart

Qgis, vector menu -> Geometry tools -> Multipart To Singlepart.

arcmap, No advance license need,