No, you cannot punch out the corners and do the bends in one press stroke. This will be done in a minimum of two strokes: First to punch out the corners, and second to do the bends.
However, unless you need to do a whole lot of volume (maybe 5,000 pieces or more), you are better off doing the bends on a press brake one at a time instead of investing in an expensive die to wipe all four flanges at once.
Regarding the tonnage needed, pretty much any press can handle this - you are not talking about any significant tonnage requirements. For punching the corners out, if you are starting with a blank that is already the exact size you need (minus the corner cutouts), you would only need around 5 tons to punch the corners out.