1.yes,you can
2.you can edit jsp files just by using notepad,and which is a question is how to run your jsp,you can download TomCat freely from the net source,and TomCat is a free container which can run jsp.
3.yes,you can,but you should download a jdk(java developer kit) and install it first.
4.yes,it's enough if you don't use tools such as websphere.and if you want to edit your jsp in JBuilder,the computer may perform slowly.