When you install by downloading from rumkin, getjar, imserba,.....you go to their download page and enter the jumpcode they gave you to start the download and install. If you installed using those services you would know what I am talking about.
The dpad is the arrows that appear on the bottom of the screen for some apps. Most apps we remove them when we can. Mostly it is used for apps that are non touch screen.
As far as making games fullscreen by removing the dpad, goatbreaking, and tkfe there are stickies on the forum to answer your questions. It is nothing that can be answered in a few lines. I will set you up with some links. Best to do some searching next time please.
Installing with tkfe (leads to other links for using it)
http://www.samsung-impression.org/index.php?topic=906.0Everything you need to know and more about goatbreaking
http://www.samsung-impression.org/index.php?topic=475.0Making apps fullscreen
http://www.samsung-impression.org/index.php?topic=981.0