24 Hours Transit Visa at Shenzhen Airport

Hello, we hold British passport, will transit in Shenzhen ,lay over 22 hrs and 12 hours on both return leg. Our trip are London - Shenzhen- Kuala Lumpur return in 10 days. My questions are:-
1) am l qualify for 24 hrs free visa transit?
2) do l need to apply two (2) times on both legs?
3) my plan is to book overnight hotel near airport for long layover, so l need to pass through immigration, is this 24 hrs visa allow me to exit airport?
4) l assume this is Free without paying fees.
Thank you for your help