Limit to One Shift, Hide Shift When Full

Hello! I was wondering if anyone had guidance on the following:

1. Is it possible to limit a user to selecting only one shift from our V4SF website sign-up page?

2. Is it possible to hide shifts from our V4SF website sign-up page once our # of Volunteers Still Needed = 0? Even with Status = Confirmed for hours, the shifts still appear on our website sign-up page as being available.