Available modification methods depend on the type of features you select.
To modify a feature, select it or create a selection set.
Gizmos
Control Points
Attributes
You can undo most changes you make within an editing session. See Reverse Your Changes.
You can also return to the state of your original data by regenerating your model. This refreshes the model with up-to-date data from the original data sources. Regenerating overrides any changes you have made, either due to sketching or adjusting features.
If the model is large, regeneration can take a long time. You can interrupt regeneration at any point. This results in a lower level of detail for areas that were not completely regenerated. You can resume the regeneration process later.