1) I know a little bit about the Gap Year people. Got one in my company and we are expecting a lot more in about Nov.
2) Yep you are expected to do everything that the rest of us do. Except deploy overseas.
3) Yeah, you will do the exact same training as I did. Except I didn't go to Singo so dunno about that bit.

haha Your gunna love Sunny camp K. haha They will absolutely monster you in the first two weeks. Stick it out for the first three weeks and see how you like it. Everyone, Everyone thinks of quitting in the first few weeks. It is designed to weed out the ones that really want to be there and the ones that think it is a pretty cool job.
4)Camera phone. Hmmm, well best not to if you can help it. As it depends on your Platoon Staff. You won't get much chance to use it though maybe once a week if your Platoon behaves itself. Gotta love the army and group punishments. haha Cameras are banned all together.
5)A SAScat hey.

Be EXTREMELY FIT. Try to do as many pushups as you can do. For your age you need 50+ to pass a basic fitness test for reg army. Do as many situps (feet held)as you can do. You need 100+ to pass. Run 2.4km in under a minute faster than your age band needs. I think for under 25s its something like 10mins.
Train for and pass the Carter Course (Special Forces barrier test).
Sign up for regular service and try and get into the recon plt of your unit.
A bit out of your control but, when you get to a unit put your hand up for courses like Reg signalers course, recon platoon selection, Combat First Aider. Basically courses that show you are above average intelligence and that you can be multi skilled. Recon because well hey that's basically what the SAS boys do.
Be mentally tough. Be the one that is the last to quit, the one that encourages others and helps others on pack marches etc. One example of the SAS mentality is carrying around 30-45Kgs of kit and a main weapon all day, do a section attack up a step hill for 800m or more (lots of sprinting a crawling). When you've gotten to the top of the hill and cleared the immediate area is where the average to good soldiers mentality differs from that to a SAS trooper. The average soldier will sit down have drink, brew up and have something to eat, then think about what to do next ie clean weapons, prep more defences. The SAScat on the other had gets to the top of that hill clears the area, prepares the defences, stands too for a bit to make sure there is no counter attack, picks up the wounded, then cleans his weapon, has a quick drink THEN thinks about sitting down and then having a feed or a rest.
Find and read accounts of the SAS in Vietnam and the 22SAS in the Falklands campaign eg goose green, the raids on the Argentine airfields, Aus SAS recon patrols in the jungles of Vietnam, Bravo 20 etc.
I know from a good source that part of the Aus SAS selection course involves hopefuls carrying around a 44gallon drum (each) with them all day while walking across country to trig points. Another selection technique is to split the hopefuls into patrol size sections (six people). Give them a bomb of a car with no wheels or something suitably heavy without wheels. The hopefuls must find a way of making the object mobile push it for an unknown length of Kms carring any injured team members with them. And perform an unknown number of tasks along the way. All with webbing, weapons, a radio and packs. I say unknown length and tasks not because I don't know but, because the hopefuls aren't told how far, how many or tasks. Another part involves being in full kit, on your own and navigating through a mountain range for kms and kms and perform tasks and answer instructors questions on the way.
Even after passing the SAS selection course you may not be accepted. There is a certain something that they look for if you pass and have it your in. If you pass and don't have it your not in.
Basically it is the most extreme, hardest thing you can do in the army bar a Fu$% fight of a combat operation.
Hope I haven't put you off hahaha

but, that is the long and the short of it.
Congrats on your letter of offer. DON'T TAKE LOTS TO KAPOOKA. You will not have a chance to use any of it. Take only what they tell you to take.