How common are regulations limiting when the FO can be PF?
All the airports listed in the AIC are quite tricky to takeoff/land in. For example, the Lengpui airport runway is a classic example of tabletop runway.



Source: www.misual.com

The Leh runway is surrounded by steep hills.



Source: geolocation.ws

The kullu airport runway has a river in both its ends.



Source: www.airportsindia.org.in

This is the reason for these restrictions. I'm not aware of any such regulatory restrictions in case of other countries. However, the operating airlines can have their own rules about (Category C) airports.