72 hr visa - order of entry & when / where to apply

Please can you confirm whether HK counts as a '1st' country before Shanghai, given it's special status?

Proposed business trip to support Chinese colleagues is;

UK -> HK -> Shenzhen (5 day VOA for HK -> Shenzhen) -> HK -> Shanghai -> UK

Also, I understand that you have to have the 72 hr free transit to landed in Shanghai, but the 72 hrs begins from when you apply for the 72 hr free transit. Where / when do you apply for the 72hr free transit?

Thanks,
Chris