find my thoughts and experiences below.
ad 1) I do use some time to frame the session right at the very beginning even before entering into check-in. for early-practice circles that seems very helpful in my impression. for me it is also about building a connection and helping people to feel in a "safe container".
ad 2) No
ad 3) all of the stated questions might help. However, one concern or recommendation: make sure you don't trigger a "justification energy" right at the beginning. the most helpful attitude for a facilitator is a neutral stance trusting the process. for me it is not best practice as facilitator to validate a tension/proposal and let the person prove that this is a valid even before entering into the process. That's rather called "heroic facilitation" which is a trap in the beginning in my experience ;-). You might ask some questions like you proposed, if a circle member requests that. But just as standard pattern it creates a weird judgemental setting. Instead, use and trust the process to do its job. Use clarifying questions and reaction round (in-process-coaching) to help the person find out, what it is about...
hope that helps.