Support for China travel

Hello!

We are a mexican married couple traveling right now in China under the Tourist L type
Our L type was granted for 60 days.

Our plan is to travel around china for two months and leave mainland china the day our L type expire to head to Hong Kong.

We will stay in Hong Kong for a week and then we need to get back to Shenzhen to take a flight to India. The flight is already booked.

• Is it possible to obtain the 5 day border single entry visa for Shenzhen special economic zone in the port of Luohu to take our flight out of China?
• Is it better to apply for the 144-hour free transit to Guangdong Province (We will travel from Hong Kong to Shenzhen by train)
• What would be the best option according to your experience?

Thanks for your support