TOPIC: Groups and preregistration

I have a few questions. We are trying to set up membership and event registration for our sport league. I understand that we can hook it up so that when the user is logged in, the form is autofilled with their CB data. That is great, but would it be possible to limit registration to ONLY people who are also members of the site (those who have active memberships)

Is it also possible to set it up so a team manager can register multiple athletes. Either by entering their id, email, or better yet have them somehow connected to the user and then they can just toggle them.

For our events we have a priority registration period, followed by an open period. Is this something we can set up, where only certain people can register during the priority period?

Thank you