Whereabouts and Check-Ins

No. It tells people you have already chosen that a check-in did not arrive. It is not a panic button, it reaches no authority, and nobody gains access to your account or documents. Do not rely on it in place of contacting the emergency services where you are.

No. They are separate features with separate settings. Your day counts stay private whatever you share about where you are, and someone invited to see your whereabouts sees nothing of your travel totals.

No. Their invitation email carries a private link that shows only what you allowed, with no account or password of their own.

Yes. The help pages cover sharing your whereabouts and setting up check-ins step by step.