I think you can talk about anything, to anyone, at any time; it is your therapist that cannot talk about you as "you" other than to you. But, if you wanted, you could tell your best friend or enemy what you think of your therapist and why just like you can tell them what you think about any other subject. Boundary rules are on the therapist. You can ask your therapist anything but your therapist is under no obligation to answer anything they don't feel is germane to your treatment.

If you see your therapist wherever, you can approach and say hello or you can ignore or you can make faces at her, whatever you feel like Or, you can ask "what should I do if we meet outside sessions?" and the two of you talk about it and mutually decide what works for the two of you.

Boundaries tend to get broken because one is thinking too hard only about one's self but boundaries often have to get broken before one can know/learn there is a boundary there. Most boundaries in therapy will get mentioned in the first few meetings with the therapist, there are no universals but often one therapist will have similar boundaries to others; yes/no to email/other contact, acting out discouraged (no "ambulance chasing"), pay on time, arrive on time, give notification of cancellation at least 24 hours ahead or pay, etc. Other than what is mentioned, the relationship evolves over time and what procedures are followed in the beginning might get changed as one goes through the process.