Hi Fafi,
I attended an Assessment Day back in April 2010 in Sydney and also made it to the group rounds and then got cut. I re-applyed and attended my Final Interview yesterday!!! I would definitely suggest re-applying because you never know!!
For your FI they ask for a contract or pay slip from your most RECENT employment so not all of the jobs you've had!
In terms of going to the assessment day 5 months after, I would either email them and ask or just go and see what they say?? I imagine they would come to Australia again in the near future as they are doing a massive recruitment at the moment.
Good luck!!!