Which of these cases are examples of third degree price discrimination?

This is correct. Timing is another characteristic that can be used to discriminate between different consumers.

This is correct. Following the concept of third degree price discrimination, the characteristics of markets should be considered when setting prices. In this case it makes sense to charge less in poorer countries than in richer countries.

This is true. In the case of third degree price discrimination the firm charges lower prices to the customers who have a lower willingness to pay (e.g. students).