Hong Kong entry permit application details

I received a reply from Mr. Nick . Thank You. However still need to clear. I tried many days to call sri Lanka embassy to get information but failure to get a call since they do not pickup the phone.
I have been to HK many times while Others not visited Hk. But have been to UK and some more countries.
Mr. Nick mentioned that with appication to get visa to HK submit the flight itinery to the embassy with the document. But without having entry permit it a risk to buy tickets since most tickets are not refundable. Could you please explain me can we submit the application without the flight itinery .Further my plan to travel from HK to Gunagzhou by bus. then to beijing by train.
our plan to buy flight and train tickets after get the entry permit. Isn't is possible ?
Naml