144 hours transit VISA free questions

I'm flying in HK and will go to Macau this Dec. I am planning to take the Ferry from Macau to Shekou Port for the 144 hours transit VISA and then from Shenzhen to HK. I have some follow up questions. 1/.When arriving at Shekou Port for the 144 VISA free transit, do we just go to the regular custom counter (international visitors) or is there a special counter we must attend first? 2/. If for some reason the 144 VISA free transit is not granted, there is still a VOA VISA offering at Shekou Port right (for backup and what hours of operation?) anything we need to pay attention to? 3/. When we leave Shenzhen to HK, we were originally planning to either get a private shuttle from Shenzhen to HK, if I have my private shuttle reservation confirmed, is that good enough for proof of return transit? (I also assumed, I do not have to exit China from the same port we enter (Shekou Port)). Our other plan is to go through Luohu and take the subway to HK (would I even able to pre-purchase a subway ticket from Luohu to HK? or do I need to purchase an express train ticket from Futian to Hong Kong? Thank you once again for your advise.