I release the Form2 in Form2.Cmd2.Click and using DO FORM Form2 to show the form.

Form1(hide Form1, show Form2) ->
Form2(hide Form2, show Form3) ->
Form3(release Form3, show Form2)->
Form2(release Form2, Show Form1)-> (I just release Form2 at this moment)
Form1(release Form1, exit program)