query on correct visa to apply for China as an Australian

I wish to return to China to see my girlfriend a few times in the next 12 months. She is a Chinese national and will of course send me an invitation like she did late last year which i acquired a 3 month single entry with (which was all i wanted at the time). On my 2nd visit this year we wish to marry. There also will be a family member (of hers that will marry in Shanghai late this year).
My question is can i apply for a 12 month multiple entry visa and do i need to show all my entries in and out of china as i would only be aware of the first trip dates when i submit the visa. i have emailed the China visa consulate about 6 times asking what i can do and what are the limitations, but all they reply every single time is it depends on my itinerary. I think they want and need all the dates of in and out of china. So do i just keep applying for 3 month visas? I just would like to have this knowledge so i do not book fligts and then have to cancel these and lose money and be forced to rebook because i booked flights for eg 15 weeks and the limit is 3 months...etc
Also, can an Australian stay longer than 3 months in one time (obviously with a visa longer than 3 months), but can one stay longer without having to leave china and then re-enter? Or, do you have to leave and re-enter every 3 months?
Thank you for your time..I look forward to your reply