A single operation adds the s-bend connector, complete with bends. You can add the second keyhole slot by dragging and dropping the first one. Inventor offers a full range of special commands with which you create and constrain a series of sheet-metal details directly, without first creating and constraining sketch profiles. Figures 4 through 8 show some of the sheet-metal capabilities, as explained in their captions. You can add more holes and flanges.
Inventor adds corner reliefs automatically.
A single click produces the flat layout, complete with bend allowances. Standard sheet-metal bend allowances are built in, but you can customize the settings so that the part unfolds correctly to the equivalent flat layout. Inventor can display the flat layout simultaneously with the 3D model, and the layout updates to reflect any editing you do to the 3D model. If you design something that is impossible to unfold, Inventor objects but won't refuse you. You can then fix the 3D part as needed.