I don't think you're a Perceiving type, just based on your word choices, proper punctuation, and lack of spelling errors. You were very specific and easy to follow. And I wouldn't worry too much about your age, as long as you don't derail threads or make trouble... some of the people in their 20's here still haven't matured enough to post intelligently, as a matter of fact.
You seem IJ-ish, but I can't really discriminate T/F or S/N. I'm gravitating towards INTJ as being likely for you based on the available information... your disorganization may be more lack of S than lack of J (since I rarely clean/organize my folders... and though I usually get work done on time, sometimes I forget or become distracted and end up rushing at the last minute.) Also, some INTJ's have a tendency to be compulsively polite, although just as many are rude.
Oh, and you probably shouldn't trust that test. It pegs practically everyone who tends to be curious and meticulous in their studies of an abstract concept as INTP. The definitions of the functions don't necessarily fall within the lines they've drawn, and I tend to think the functional order test is intrinsically flawed in crucial ways.