My small contribution on the ‘stall’ topic, based on 7+ years of engineering flight testing on Part 23/25 aircraft.
First of all, it is not only the Regulation (FAR/Part 23 or FAR/Part 25) which determines the ways in which a stall should be investigated : the basic guide for the authority is the Advisory Circular AC23-8 or 25-8 (and the equivalent for the EASA side). Here you can see how many types or stall stall entries etc should be investigated for the handling quality side. Having cleared the handling, normally you proceed with the performance side To demonstrate good handling , you need to investigate very slow entries (<< 1 kts/sec), 1 g entries (close to 1 kts/sec) and fast entries (3-5 kts/sec) . it is interesting to note that the fast entries do not normally correspond to an accelerated entry (>> 1 g), as the manoeuvrability of whatever a/c at those low starting speeds (trimmed at 1.3 stall speed) do not allow to load many g’s.
The different entry decelerations allows also to interpolate the nominal 1 kts/sec entry speed, which is normally the ‘performance’ stall speed. It is interesting to note that , contrary to common sense, very often the ‘fast deceleration’ entry is more predictable and more straightforward than the 1 kts/s entry, with less wing drop, etc. Low deceleration stalls at 35000+ ft are often more strange, with hard wing drop and less clean nose pitching.
Power-on stall can sometimes results in very, very high deck angles, with an usual marked wing drop at the break.
For multiengine, the OEI stall with the other at 75% power is… frightening (at least, I always was frightened), because , though the VMC should have been already investigated and cleared, stall speed and VMC are often too close to allow to remain … relaxed . For FAR /Part 25 a/c , the performance determination of the stall speed is even more complicated (use of trailing cones, precision pitot tubes, etc to measure the exact static / total pressure). This is due to the fact that all runway speeds( and, as consequence, take-off and landing performance) are factored over the stall speed in TO configuration ( plus other speeds as VMCG, etc) .
For what refers to the post stall spin, I am pretty confident that, even 50 years ago during the C150 certification, being AC 23-8 already in use in its primitive form, quite all types of spins have been investigated ( at least those with the W & CG inside the promulgated envelope), and for the C152 Aerobat also those with a negative AoA ( being that aircraft certificated in the acrobatic category).
Note also that , for single engine aircraft, the spin, and its different spin entries, should be investigated anyway , which implies a matrix of many configurations (power/flaps/landing gear/weight/CG) . Recently Cessna lost two prototypes of their new trainer aircraft in spin investigation/certification, though not intending to certify it in the acrobatic category.
In the ’70, I learned to fly on a C150 with floats ; my AUW was 82 kg, hopefully the instructor was , and still is, smaller than me. Training lessons were 00:50 each, and after two lessons we needed to refuel. Waves / OAT affected veeeery much the take off run, sometimes in summer we counted 80 seconds between power application and take-off ! But I still think that, for basic training (also for learning seaplane technique) is one of the best aircraft .
Having learned take-off and landings on a 50 km long / 3 km wide runway (=lake) , I had lot of difficulties , when I transitioned on land planes, to align during landing with the runway, which was now very narrow and short compared to that on which I learned to fly……