Multiple entry transit visa

It depends entirely of the immigration officer if he will give you a temporary permit or not to leave the airport.
14 hours is a long layover so I'm sure they'll give you one but there's really no guarantee.

On your way back you're eligible for the 144h twov if your layover is longer as 24 hours.
It doesn't exist a 72h twov anymore in Beijing and it's not a visa, it's a transit without any kind of visa.