To be able to shoot the blue portal gun, you must aquire it. To do so, goto testchamber 2 and, you will find the portal gun. Simply reach it, by steping through the portal it shoots, and then grab...
no, portal, (unlike its newer, more interactive counterpart) is not as good as portal 2, portal only has solving much more difficult tests, and, although they are funny, a few comments by GLaDOS,...