Zener voltage for protection of GPIO

Do you mean, like, the MCU could output 5.1 or 5.2 V?

The 10K resistor is to pull the gate low in case the MCU pin is floating. Why should it be on the other side of the 200 ohm resistor?

I don't understand the idea of putting a Schottky diode from the pin to VCC.

Someone mentioned optocouplers so I'm looking at those now. Maybe TLP155E: https://datasheet.lcsc.com/lcsc/1809191915_TOSHIBA-TLP155E-TPL-E_C56499.pdf