Hi Kranthi,
webdynpro framework allows you to use only 3 kinds of button types. you cant have four.see the screen shots attached.Image may be NSFW.
Clik here to view.Image may be NSFW.
Clik here to view.
These are the standard buttons given by framework. If you want more than 3 go for your custom development as suggested by Ramakrishnappa Gangappa .
Regards,
Ravikiran.K