1. No. A passive infrared (PIR) sensor can only detect abstract movement. You will need an active-type infrared sensor or a device like a thermal camera (and a lot more complex code) to extract richer movement information.
2. An ultrasonic sensor measures the round-trip timing of ultrasonic pulses, which is then used to calculate distance. Factors that affect the ultrasonic pulse timing or the speed-of-sound constant used therefore affect the calculated distance. Some examples include temperature since this affects the speed of sound, the material of the detected object (for example, does it absorb sound?), the size of the object, and its angle relative to the sensor.
3. Both latching and non-latching Hall effect sensors output a digital signal – their output pin is either HIGH or LOW. In contrast, ratiometric Hall effect sensors output an analog signal (varying voltage) relative to how close they are to a magnetic field.
4. The callback_handler...