As far as I understood, the four tetrads are done in a sequence, without choosing. After rapture arises in Kayanupassana, rapture
becomes the object of meditation, and the transition from kaya to
The above is how I interpret what was said from from 51:30. What was said was the previous satipatthana supports the next satipatthana. In other words, developing calming the body supports the arising of & profound sensitivity of rapture.
the four Satipatthanas are always investigated.
This statement by Santikaro was vague. It all depends on how profoundly or how shallowly the practise is. In daily life, the satipatthana practise will generally be quite shallow or superficial (unless a person has previously developed samadhi, which they can enter, at will, while sitting on a bus or in a boring office meeting). Once there is a question about "daily life", the answer will not be particularly profound. For example, in daily life, the 1st tetrad will generally not be developed to give rise to rapture of the 2nd tetrad. Reaching rapture is generally has the requirement of formal retreat. In daily life, the framework in MN 10 rather than MN 118 would probably be best followed.