Good news guys!!!
My Visa got approved this morning! after 21 months of waiting finally got approved.
I have been checking the status on immi account after uploaded everything. There are a few thing I could confirm(based on my case):
1, The status actually CAN change from "RECEIVED" directly to "FINALISED".
2, After received the s56 message, it appears to me that they might put your case aside and wait for 28days, then they reopen it and assess the application based on the info you provided.
3, The CO who send the s56 message was not the same CO who grants the visa.
Again all above are based on my case, it might different to yours. I just thought I should provide some ideas for those still await.
Last but not the least, thanks for this forum and thanks for all those kind people who helped me. Wish all the best to all of you