Hey @joan1,
1. Yes, anyone with the link can view your staging pages or preview pages even if they’re not user in your Hubspot account
2. Yes, but not by IP (although this is possible with some custom JS). An easier solution would be to set the page to private with a password in Settings > Advanced options. Just share the password with whoever you want to view the page
3. You can have a different staging environment for each of the domains you have connected to your Hubspot account but I don’t think you can publish to all from one, so yes you’d have to create 5 different staging sites (unless @dennisedson knows something I don’t, which he often does)