Apologies if this is too off topic to IVZ, but I'm new to the...

Apologies if this is too off topic to IVZ, but I'm new to the ASX and this is the only stock I own in Australia. This seemed like a somewhat appropriate thread to be asking this question, but let me know if there is a better place. The questions are with regards to the bid/ask spread:
* Are the orders filled in the order in which they are received? For example, I currently have a buy order in for Invictus for 57,000 shares at $0.125 AUD. Will my order be filled once the orders that were placed prior to mine are filled? Furthermore, will all buy orders at $0.125 placed after mine be filled after my order is filled or will some jump ahead of it?
* If not, how is the sequence of the orders being filled determined? Is it somewhat random?
* Do certain entities get priority in having their orders filled over the average retail buyer/seller?
* Are orders placed via international brokers a lower priority in the fill order (I use Fidelity's international trading option and live in the USA)

Any additional insight into how the ASX works would be much appreciated, particularly with regards to the above. I'm based in the US and this is the first stock I've purchased on an international exchange. If there are any links to resources that would be helpful in answering questions like the above, please let me know. I've done a little reading but couldn't find an answer to the above.

Thanks in advance!