I am an Australian citizen. Arriving at Beijing Capital Airport via overnight transit in Singapore.

I will be sightseeing within the Beijing area for 3 nights and then leaving on a cruise out of Tianjin back to Singapore. The first country on the cruise is Japan. I understand it is only the last country before arriving and the first after leaving, that is considered by Immigration when granting the 144 hr Transit Visa and under the new 144 Hour rules, it is acceptable to arrive and depart from a different location (within the BJ/Tianjin Province) as per my above plans?
I also read that the 72 hour Visa only allows me to enter and leave via the same airport and strictly speaking, i'll be in transit less than 72 Hrs. Would Immigration therefore try to apply the 72 Hr rules or has the 144 Hr visa virtually replaced the 72 Hr visa?

Thanks
Rob