When you launch your game you should get a window showing graphics and input settings. Under graphics there is a checkbox named "windowed" that lets you toggle between whether to launch the app in fullscreen.
If you don't get the graphics and input screen then you might have checked "Only show this if the option key is down"..Not sure which key is the option key =) hope this was a little helpful
Why No matter how i choose the resolution
640x480
720x480
720x576
800x600
1024x768
1152x864
1280x720
1280x768
1280x800
1280x1024
1360x768
1440x900 or check or didnt check the Window mode