The rules, in order. A circle ExpressAgain made complimentary is on the Family plan for good (see Complimentary plans). If an organization or health plan sponsors the circle, the family is not asked (see Sponsorship). A circle activated with a founder code is active for good. While there is no way to pay yet, nobody is gated at all — there is no paywall without a way to pay, and neither the plan pages nor the invite limits close anything. Circles created before billing existed are grandfathered on the Family plan and never put on a trial clock. A circle created after launch has a seven-day trial from the day the owner account was created.
Once there is a way to pay in the app, a page that belongs to a higher plan says which plan it is on, with See plans for the account owner. Nobody already in a circle is ever removed when a plan's invite limit would apply; the circle just cannot add more until it moves up.
The whole thing fails open on purpose: any uncertainty grants access. A billing glitch must never lock a family out of a sick relative's circle.