Some Questions about Shenzhen Visa on Arrival

I am an Iranian and I’ve planned to enter to Shenzhen through Shekou Port after leaving Hong Kong international airport by a ferry. I want to apply for a Shenzhen Visa on arrival, however, I have some doubt about that

1- Can single travelers get Shenzhen VOA or they must join to a tourist group from Hongkong to be eligible?

2- Can I leave Shenzhen after passing five days through Shenzhen airport (to Beijing and directly from there to Tehran) or I must leave Shenzhen through the Shekou port again?