The below code snippet shows renaming the existing feature name with new name for point, alignment, profile, and corridor.

//Required References
using Bentley.CifNET.GeometryModel.SDK;
using Bentley.CifNET.SDK.Edit;

public void RenameFeatureName()
        {
            //Get active DGN model connection for edit purpose  
            Bentley.CifNET.SDK.Edit.ConsensusConnectionEdit con = ConsensusConnectionEdit.GetActive();
            if (con == null) return;

            //Get active geometric model
            GeometricModel activeGM = con.GetActiveGeometricModel();

            //Rename point feature
            foreach (PointEntity2d point in activeGM.PointEntities2d)
            {
                if (point != null)
                {
                    //Rename point feature name, this is for OpenRoads Designer version 10.11 
                    //bool status = point.SetFeatureDefinition("PointRenamed");

                    //Rename point feature name, this is for OpenRoads Designer version 10.12 and above
                    bool status = point.SetFeatureDefinition("Point\\Existing\\Right of Way\\E_Existing_RW", "PointRenamed");
                    break;
                }
            }


            //Rename alignment
            foreach (Alignment alignment in activeGM.Alignments)
            {
                if (alignment != null && alignment.IsFinalElement)
                {
                    //Rename alignment feature name
                    string renamedName = alignment.SetName("AlignmentRenamed");
                    break;
                }
            }

            //Rename profile
            foreach (Alignment alignment in activeGM.Alignments)
            {
                if (alignment != null && alignment.IsFinalElement)
                {
                    foreach (Profile profile in alignment.Profiles)
                    {
                        if (profile.IsFinalElement)
                        {
                            string name = profile.Name;
                            //Rename profile feature name
                            bool status = profile.SetFeatureDefinition("Alignment\\Geom_Baseline", "ProfileRenamed");
                            break;
                        }
                    }
                }
            }

            //Rename corridor
            foreach (Corridor corridor in activeGM.Corridors)
            {
                if (corridor != null)
                {
                    //rename corridor feature name with "CorridorRenamed"
                    corridor.FeatureName = "CorridorRenamed";
                    break;

                }
            }
        }