Can you choose your desires?

In my opinion it depends how broadly 'desires' is defined. You could use your freedom to choose your actions to build a system that Pavlov's you toward or away from some specific things, but it wouldn't let you escape the underlying 'I'm addicted to dopamine' drive that is underlying any agentic entity. This question is interesting not just from behavioral science or psychology perspective but also from AI perspective.

Partially. Certainly your desires can change over time.

Define desire - in anorexia, for example, is the victim choosing his desire to not eat, or is he not eating despite desiring it, or something else